Abstract We investigate the magnetization dynamics through magnetoimpedance effect in films of fe... more Abstract We investigate the magnetization dynamics through magnetoimpedance effect in films of ferrimagnetic insulator yttrium iron garnet capped by copper. Thereby, we explore the magnetoimpedance in systems with magnetic insulators by varying the thickness of the magnetic material, and probe current frequency. We observe that the difference of electrical nature of the layers composing the films gives rise to the magnetoinductive effect in the whole frequency range, as well as favors the appearance of the ferromagnetic resonance effect even at low frequencies. We discuss the experimental results in terms of the structural features of the magnetic material, its magnetic properties, and the different mechanisms governing the magnetization dynamics. The results place the films of ferrimagnetic insulator yttrium iron garnet capped by copper exhibiting magnetoimpedance effect as very attractive candidates for application as probe element in magnetic sensors operating at low frequencies and with energy-efficient technologies. Further, we disclose an auspicious technique to look at the magnetization dynamics in magnetic materials and we provide a new perspective to solve questions related to the integration of insulator ferrimagnetic materials with the coplanar waveguide in broadband frequency applications.
Thermomagnetic properties and magnetocaloric effect (MCE) in Ni 50.3 Mn 36.5 Sn 13.2 Heusler allo... more Thermomagnetic properties and magnetocaloric effect (MCE) in Ni 50.3 Mn 36.5 Sn 13.2 Heusler alloy ribbons are reported. Large magnetocaloric response has been obtained for l 0 H = 3 T in both the reversible adiabatic change in temperature DT ad (À6.3 and +4.7 K) and the isothermal change in the total entropy DS T (+11.8 and À2.2 J K À1 kg À1), respectively at the temperature T str = 271 K at which the magnetostructural phase transition from the low-temperature Martensite phase (MP) to the high-temperature Austenite phase (AP) takes place, and at T CA = 311 K at which the magnetic phase transition in the AP occurs. The MCE has been studied through the Stoner's magnetocaloric parameter n S (Stoner EC. Phil Mag 19 (1935) 565), and a generalized expression for the equations of state for magnetic materials is presented. The phase coexistence of the MP and AP has been studied via their respective sublattice with opposite-aligned magnetic moments by means of the effective magnetic anisotropy density e A induced by the supercooled (superheated) secondary AP (MP) in the MP (AP). Magnetic fields higher than the critical value of l 0 H R = 0.5 T produce alignment of the two magnetic moments and hence a change in the magnetic ordering in the MP from antiferromagnetic to ferromagnetic, resulting in a thermomagnetic behavior in which the field-cooling and field-heating magnetizations become coincident, the induced anisotropy vanishes e A = 0 and the metastability disappears. New tentative methods to obtain the spontaneous magnetization of both MP and AP and their respective fractions in the phase coexistence range are reported.
Journal of Spintronics and Magnetic Nanomaterials, 2012
Highly ordered (Fe, Co and Ni)-Pd nanowires arrays have been synthesized by means of electrochemi... more Highly ordered (Fe, Co and Ni)-Pd nanowires arrays have been synthesized by means of electrochemical deposition processes into the pores of nanoporous alumina membranes employed as templates. Nanowires have a diameter about 66 nm, 105 nm of inter-wires distance and length ranging between 500 nm up to around 1 m, depending on the efficiency of the electrochemical deposition process. The Pd content in the alloy for each type of nanowires array has been found to be dependent on the specific ferromagnetic transition metal co-deposited at a fixed electrodeposition current density, due to their different respective standard electrode potentials. In addition, structural characterizations performed at room temperature and magnetic measurements indicate a clear dependence of basic physical parameters of the nanowires studied, such as their microstructure, coercivity, reduced remanence and effective anisotropy field, on both the relative amount of Pd and the kind of ferromagnetic transition metal co-deposited in the resulting alloy. Thermomagnetic ZFC-FC-FH measurements indicate the existence of ferromagnetic shape memory behavior for the arrays of nanowires of the Fe-Pd alloy.
We investigate the direct and inverse magnetocaloric effect in Ni 45.5 Mn 43.0 In 11.5 Heusler al... more We investigate the direct and inverse magnetocaloric effect in Ni 45.5 Mn 43.0 In 11.5 Heusler alloy ribbons comparing the results obtained for the as-quenched sample with the ones after different annealing procedures. An enhancement and shift of the entropy maximum to near room temperature is observed in all annealed samples. A remarkable magnetocaloric effect is observed in samples with short-time treatment (10 minutes) and at the lowest annealing temperature. We show that the suppressing of uncompensated martensitic transition and thermal hysteresis are both influenced by the heat treatment. Also, an improvement on Curie's temperature is observed and, at low magnetic field, it has been risen up to 310 K. Our results demonstrate that the martensitic transformation is highly sensitive to the applied magnetic field and also to the annealing treatment, which means that the magnetocaloric effect can be tuned showing different behaviors for each sample.
The magnetic properties of sub-micrometric magnetic structures of Ni and permalloy (Ni 80 Fe 20) ... more The magnetic properties of sub-micrometric magnetic structures of Ni and permalloy (Ni 80 Fe 20) patterned stripes are studied as functions of temperature. The samples are produced by combining an interferometric lithographic technique with sputtering. At room temperature, ferromagnetic resonance and hysteresis data indicate the existence of an in-plane uniaxial anisotropy in both samples. The NiFe sample has an easy axis along the stripes direction in the entire studied temperature range (2 < T < 300 K). On the other hand, an interesting change in the easy magnetization direction is observed in Ni samples, from parallel to perpendicular to the axis of the stripes, when the temperature is decreased. The results are interpreted in terms of a competition between shape and magnetoelastic anisotropies.
Ordered arrays of ferromagnetic nanowires with (Fe, Co)-Pd compositions have been fabricated from... more Ordered arrays of ferromagnetic nanowires with (Fe, Co)-Pd compositions have been fabricated from a chloride based electrochemical baths by means of template-assisted electrodeposition into self-assembled nanopores of anodic alumina membranes. The nanowires have a diameter and inter-spacing distance of 72 nm and 105 nm, respectively, and around 0.6-1.6 m in length. Their microstructure and basic magnetic properties are reported. Coercivity, remanence and respective angular dependences on the applied field up to ± 3 T have been determined from room temperature hysteresis loops measured in a VSM. The study has been performed paying particular attention to the influence of increasing from about 27 up to 63 percent the Pd content in the nanowire alloy.
The magnetic properties of Co, Ni and NiFe sub-micrometric structures produced by holographic lit... more The magnetic properties of Co, Ni and NiFe sub-micrometric structures produced by holographic lithography and sputtering techniques are investigated. The structures were obtained using a mask previously recorded by holography in a photo-resist film coated on a quartz substrates. After this procedure, the magnetic material was deposited using the sputtering technique, and the photo resist was removed by lift-off. Samples with thicknesses of around 500 Å were grown in stripes structures and periodicity of 800 nm. The results indicate that the samples with Co and NiFe present exchange bias effect and this is due the surface oxidation.
Heusler alloy Ni 50.0 Mn 35.5 In 14.5 ribbons were prepared by melt-spinning technique. Several s... more Heusler alloy Ni 50.0 Mn 35.5 In 14.5 ribbons were prepared by melt-spinning technique. Several short time annealings were carried out in order to enhance the exchange bias effect in this alloy ribbon. The magnetic transition temperature increases with the annealing, compared to the as-spun sample, however no significant differences in respective Curie temperatures were observed for austenite and martensite phases in such annealed samples. Exchange bias effect is observed at low temperatures for all samples and practically vanishes at 60 K for the as-spun sample, whereas for the annealed ribbons it vanishes at 100 K.
The size effects on magnetic properties of nanowires arrays were studied varying the nanowires di... more The size effects on magnetic properties of nanowires arrays were studied varying the nanowires diameter and maintaining the same periodicity among them, for two different nominal compositions of Co and Ni in the alloy form. The competition among magnetocrystalline and shape anisotropies changes drastically from smallest to biggest diameters altering the easy axis direction. In the case of 75% of Co in alloy, experimental values of the effective anisotropy constant (K eff) vary from positive to negative depending on the diameter, which means a reversal of the easy axis direction. For 50% of Co the shape anisotropy dominates over the magnetocrystalline for all studied diameters.
Temperature dependence of longitudinal coercivity, H c // , for (a) Co (1Àx) Pd x and (b) Co (1Ày... more Temperature dependence of longitudinal coercivity, H c // , for (a) Co (1Àx) Pd x and (b) Co (1Ày) Ni y nanowire arrays. 07A325-3 Vivas et al.
Nanostructured polymer (polymethyl methacrylate) has been fabricated replicating the hexagonal sy... more Nanostructured polymer (polymethyl methacrylate) has been fabricated replicating the hexagonal symmetry ordering of an anodized Al template. A magnetic material, in this case Co, is then sputtered onto the polymer surface giving rise to a nanostructured surface thin layer keeping the high ordering induced by the precursor template. The study of this magnetic nanostructure allows one to conclude the presence
Co thin films deposited by sputtering onto nanostructured polymer ͓poly͑methyl methacrylate͔͒ wer... more Co thin films deposited by sputtering onto nanostructured polymer ͓poly͑methyl methacrylate͔͒ were prepared following replica-antireplica process based on porous alumina membrane. In addition, different capping layers were deposited onto Co nanohills. Morphological and compositional analysis was performed by atomic force microscopy and x-ray photoemission spectroscopy techniques to obtain information about the surface characteristics. The observed asymmetry in the magnetization reversal process at low temperatures is ascribed to the exchange bias generated by the ferromagnetic-antiferromagnetic interface promoted by the presence of Co oxide detected in all the samples. Especially relevant is the case of the Cr capping, where an enhanced magnetic anisotropy in the Co/Cr interface is deduced.
ABSTRACT The transport and magnetic properties of ferromagnetic shape memory alloy of nominal com... more ABSTRACT The transport and magnetic properties of ferromagnetic shape memory alloy of nominal composition Ni46Mn41In13 are reported. The alloy undergoes martensitic phase transition (MPT) around 240 K. The region around this structural transition is found to be highly metastable and susceptible to the applied magnetic field. Giant negative magnetoresistance (∼ −64% at 70 kOe) is observed in the vicinity of the thermally driven MPT. The existence of large inverse magnetocaloric effect around the MPT is also confirmed by the direct measurement using modulated ac field technique. The sample shows large exchange bias at low temperature. The role of Mn–Mn intersite antiferromagnetic correlation is discussed for the above magneto-functional behaviors.
ABSTRACT A Heusler Ni45.5Mn43.0In11.5 alloy has been prepared by arc melting and produced in a ri... more ABSTRACT A Heusler Ni45.5Mn43.0In11.5 alloy has been prepared by arc melting and produced in a ribbon shape by rapid solidification using melt spinning technique. Structural properties have been investigated, at different temperatures, by using X-ray diffraction. Austenite is the stable phase at room temperature with a L21 cubic crystal structure. Exchange bias effect was observed after field cooling by means of hysteresis loop measurements. At 5 K, hysteresis loop shifts along the axis of the applied magnetic field and that shift magnitude decreases significantly with increasing temperature. A piece of ribbon was annealed at 973 K during 10 min in order to investigate the influence of annealing on crystal structure and magnetic properties. After annealing, a martensitic phase with a monoclinic 10M structure at room temperature is observed. The onset of the martensitic phase transformation shifts to 365 K, temperatures associated with both martensitic and reverse transitions do not change noticeably under an applied magnetic field up to 30 kOe, and a drastic decrease on magnetization is observed in comparison with the as-quenched ribbon meanwhile the exchange bias effect is enhanced.
The fabrication and the study of the magnetic properties of CoCrPt/Ti nanostructures produced by ... more The fabrication and the study of the magnetic properties of CoCrPt/Ti nanostructures produced by sputtering onto ordered polymer templates are reported here. Samples exhibit a significant outof-plane component of the magnetization higher than for planar films, and it is stronger for the thicker CoCrPt films, and for nanostructured films with the shorter period ordering. The shape of the polymeric templates plays an important role for the determination of magnetic easy-axis. Magnetic Force Microscopy images of the samples show a single magnetic domain structure with high outof-plane anisotropy for the samples with longer ordering (480 nm period).
The magnetic properties of radially-oriented Co, Ni, and CoNi alloy nanowires synthesized by puls... more The magnetic properties of radially-oriented Co, Ni, and CoNi alloy nanowires synthesized by pulsed electrodeposition into porous alumina structures are measured and compared with those of similar nanowires grown in a planar geometry. The alloy composition affects the anisotropy axis direction, which is determined by the balance between the magnetocrystalline and shape anisotropies, lying transverse to the nanowires for Co samples and along the nanowire axis for Ni. Monte Carlo simulations were performed to model the magnetic hysteresis of the radiallyoriented and planar geometry nanowires using an approach based on a conical distribution of anisotropies. The model provides an excellent fit compared with experimental hysteresis loops.
Abstract We investigate the magnetization dynamics through magnetoimpedance effect in films of fe... more Abstract We investigate the magnetization dynamics through magnetoimpedance effect in films of ferrimagnetic insulator yttrium iron garnet capped by copper. Thereby, we explore the magnetoimpedance in systems with magnetic insulators by varying the thickness of the magnetic material, and probe current frequency. We observe that the difference of electrical nature of the layers composing the films gives rise to the magnetoinductive effect in the whole frequency range, as well as favors the appearance of the ferromagnetic resonance effect even at low frequencies. We discuss the experimental results in terms of the structural features of the magnetic material, its magnetic properties, and the different mechanisms governing the magnetization dynamics. The results place the films of ferrimagnetic insulator yttrium iron garnet capped by copper exhibiting magnetoimpedance effect as very attractive candidates for application as probe element in magnetic sensors operating at low frequencies and with energy-efficient technologies. Further, we disclose an auspicious technique to look at the magnetization dynamics in magnetic materials and we provide a new perspective to solve questions related to the integration of insulator ferrimagnetic materials with the coplanar waveguide in broadband frequency applications.
Thermomagnetic properties and magnetocaloric effect (MCE) in Ni 50.3 Mn 36.5 Sn 13.2 Heusler allo... more Thermomagnetic properties and magnetocaloric effect (MCE) in Ni 50.3 Mn 36.5 Sn 13.2 Heusler alloy ribbons are reported. Large magnetocaloric response has been obtained for l 0 H = 3 T in both the reversible adiabatic change in temperature DT ad (À6.3 and +4.7 K) and the isothermal change in the total entropy DS T (+11.8 and À2.2 J K À1 kg À1), respectively at the temperature T str = 271 K at which the magnetostructural phase transition from the low-temperature Martensite phase (MP) to the high-temperature Austenite phase (AP) takes place, and at T CA = 311 K at which the magnetic phase transition in the AP occurs. The MCE has been studied through the Stoner's magnetocaloric parameter n S (Stoner EC. Phil Mag 19 (1935) 565), and a generalized expression for the equations of state for magnetic materials is presented. The phase coexistence of the MP and AP has been studied via their respective sublattice with opposite-aligned magnetic moments by means of the effective magnetic anisotropy density e A induced by the supercooled (superheated) secondary AP (MP) in the MP (AP). Magnetic fields higher than the critical value of l 0 H R = 0.5 T produce alignment of the two magnetic moments and hence a change in the magnetic ordering in the MP from antiferromagnetic to ferromagnetic, resulting in a thermomagnetic behavior in which the field-cooling and field-heating magnetizations become coincident, the induced anisotropy vanishes e A = 0 and the metastability disappears. New tentative methods to obtain the spontaneous magnetization of both MP and AP and their respective fractions in the phase coexistence range are reported.
Journal of Spintronics and Magnetic Nanomaterials, 2012
Highly ordered (Fe, Co and Ni)-Pd nanowires arrays have been synthesized by means of electrochemi... more Highly ordered (Fe, Co and Ni)-Pd nanowires arrays have been synthesized by means of electrochemical deposition processes into the pores of nanoporous alumina membranes employed as templates. Nanowires have a diameter about 66 nm, 105 nm of inter-wires distance and length ranging between 500 nm up to around 1 m, depending on the efficiency of the electrochemical deposition process. The Pd content in the alloy for each type of nanowires array has been found to be dependent on the specific ferromagnetic transition metal co-deposited at a fixed electrodeposition current density, due to their different respective standard electrode potentials. In addition, structural characterizations performed at room temperature and magnetic measurements indicate a clear dependence of basic physical parameters of the nanowires studied, such as their microstructure, coercivity, reduced remanence and effective anisotropy field, on both the relative amount of Pd and the kind of ferromagnetic transition metal co-deposited in the resulting alloy. Thermomagnetic ZFC-FC-FH measurements indicate the existence of ferromagnetic shape memory behavior for the arrays of nanowires of the Fe-Pd alloy.
We investigate the direct and inverse magnetocaloric effect in Ni 45.5 Mn 43.0 In 11.5 Heusler al... more We investigate the direct and inverse magnetocaloric effect in Ni 45.5 Mn 43.0 In 11.5 Heusler alloy ribbons comparing the results obtained for the as-quenched sample with the ones after different annealing procedures. An enhancement and shift of the entropy maximum to near room temperature is observed in all annealed samples. A remarkable magnetocaloric effect is observed in samples with short-time treatment (10 minutes) and at the lowest annealing temperature. We show that the suppressing of uncompensated martensitic transition and thermal hysteresis are both influenced by the heat treatment. Also, an improvement on Curie's temperature is observed and, at low magnetic field, it has been risen up to 310 K. Our results demonstrate that the martensitic transformation is highly sensitive to the applied magnetic field and also to the annealing treatment, which means that the magnetocaloric effect can be tuned showing different behaviors for each sample.
The magnetic properties of sub-micrometric magnetic structures of Ni and permalloy (Ni 80 Fe 20) ... more The magnetic properties of sub-micrometric magnetic structures of Ni and permalloy (Ni 80 Fe 20) patterned stripes are studied as functions of temperature. The samples are produced by combining an interferometric lithographic technique with sputtering. At room temperature, ferromagnetic resonance and hysteresis data indicate the existence of an in-plane uniaxial anisotropy in both samples. The NiFe sample has an easy axis along the stripes direction in the entire studied temperature range (2 < T < 300 K). On the other hand, an interesting change in the easy magnetization direction is observed in Ni samples, from parallel to perpendicular to the axis of the stripes, when the temperature is decreased. The results are interpreted in terms of a competition between shape and magnetoelastic anisotropies.
Ordered arrays of ferromagnetic nanowires with (Fe, Co)-Pd compositions have been fabricated from... more Ordered arrays of ferromagnetic nanowires with (Fe, Co)-Pd compositions have been fabricated from a chloride based electrochemical baths by means of template-assisted electrodeposition into self-assembled nanopores of anodic alumina membranes. The nanowires have a diameter and inter-spacing distance of 72 nm and 105 nm, respectively, and around 0.6-1.6 m in length. Their microstructure and basic magnetic properties are reported. Coercivity, remanence and respective angular dependences on the applied field up to ± 3 T have been determined from room temperature hysteresis loops measured in a VSM. The study has been performed paying particular attention to the influence of increasing from about 27 up to 63 percent the Pd content in the nanowire alloy.
The magnetic properties of Co, Ni and NiFe sub-micrometric structures produced by holographic lit... more The magnetic properties of Co, Ni and NiFe sub-micrometric structures produced by holographic lithography and sputtering techniques are investigated. The structures were obtained using a mask previously recorded by holography in a photo-resist film coated on a quartz substrates. After this procedure, the magnetic material was deposited using the sputtering technique, and the photo resist was removed by lift-off. Samples with thicknesses of around 500 Å were grown in stripes structures and periodicity of 800 nm. The results indicate that the samples with Co and NiFe present exchange bias effect and this is due the surface oxidation.
Heusler alloy Ni 50.0 Mn 35.5 In 14.5 ribbons were prepared by melt-spinning technique. Several s... more Heusler alloy Ni 50.0 Mn 35.5 In 14.5 ribbons were prepared by melt-spinning technique. Several short time annealings were carried out in order to enhance the exchange bias effect in this alloy ribbon. The magnetic transition temperature increases with the annealing, compared to the as-spun sample, however no significant differences in respective Curie temperatures were observed for austenite and martensite phases in such annealed samples. Exchange bias effect is observed at low temperatures for all samples and practically vanishes at 60 K for the as-spun sample, whereas for the annealed ribbons it vanishes at 100 K.
The size effects on magnetic properties of nanowires arrays were studied varying the nanowires di... more The size effects on magnetic properties of nanowires arrays were studied varying the nanowires diameter and maintaining the same periodicity among them, for two different nominal compositions of Co and Ni in the alloy form. The competition among magnetocrystalline and shape anisotropies changes drastically from smallest to biggest diameters altering the easy axis direction. In the case of 75% of Co in alloy, experimental values of the effective anisotropy constant (K eff) vary from positive to negative depending on the diameter, which means a reversal of the easy axis direction. For 50% of Co the shape anisotropy dominates over the magnetocrystalline for all studied diameters.
Temperature dependence of longitudinal coercivity, H c // , for (a) Co (1Àx) Pd x and (b) Co (1Ày... more Temperature dependence of longitudinal coercivity, H c // , for (a) Co (1Àx) Pd x and (b) Co (1Ày) Ni y nanowire arrays. 07A325-3 Vivas et al.
Nanostructured polymer (polymethyl methacrylate) has been fabricated replicating the hexagonal sy... more Nanostructured polymer (polymethyl methacrylate) has been fabricated replicating the hexagonal symmetry ordering of an anodized Al template. A magnetic material, in this case Co, is then sputtered onto the polymer surface giving rise to a nanostructured surface thin layer keeping the high ordering induced by the precursor template. The study of this magnetic nanostructure allows one to conclude the presence
Co thin films deposited by sputtering onto nanostructured polymer ͓poly͑methyl methacrylate͔͒ wer... more Co thin films deposited by sputtering onto nanostructured polymer ͓poly͑methyl methacrylate͔͒ were prepared following replica-antireplica process based on porous alumina membrane. In addition, different capping layers were deposited onto Co nanohills. Morphological and compositional analysis was performed by atomic force microscopy and x-ray photoemission spectroscopy techniques to obtain information about the surface characteristics. The observed asymmetry in the magnetization reversal process at low temperatures is ascribed to the exchange bias generated by the ferromagnetic-antiferromagnetic interface promoted by the presence of Co oxide detected in all the samples. Especially relevant is the case of the Cr capping, where an enhanced magnetic anisotropy in the Co/Cr interface is deduced.
ABSTRACT The transport and magnetic properties of ferromagnetic shape memory alloy of nominal com... more ABSTRACT The transport and magnetic properties of ferromagnetic shape memory alloy of nominal composition Ni46Mn41In13 are reported. The alloy undergoes martensitic phase transition (MPT) around 240 K. The region around this structural transition is found to be highly metastable and susceptible to the applied magnetic field. Giant negative magnetoresistance (∼ −64% at 70 kOe) is observed in the vicinity of the thermally driven MPT. The existence of large inverse magnetocaloric effect around the MPT is also confirmed by the direct measurement using modulated ac field technique. The sample shows large exchange bias at low temperature. The role of Mn–Mn intersite antiferromagnetic correlation is discussed for the above magneto-functional behaviors.
ABSTRACT A Heusler Ni45.5Mn43.0In11.5 alloy has been prepared by arc melting and produced in a ri... more ABSTRACT A Heusler Ni45.5Mn43.0In11.5 alloy has been prepared by arc melting and produced in a ribbon shape by rapid solidification using melt spinning technique. Structural properties have been investigated, at different temperatures, by using X-ray diffraction. Austenite is the stable phase at room temperature with a L21 cubic crystal structure. Exchange bias effect was observed after field cooling by means of hysteresis loop measurements. At 5 K, hysteresis loop shifts along the axis of the applied magnetic field and that shift magnitude decreases significantly with increasing temperature. A piece of ribbon was annealed at 973 K during 10 min in order to investigate the influence of annealing on crystal structure and magnetic properties. After annealing, a martensitic phase with a monoclinic 10M structure at room temperature is observed. The onset of the martensitic phase transformation shifts to 365 K, temperatures associated with both martensitic and reverse transitions do not change noticeably under an applied magnetic field up to 30 kOe, and a drastic decrease on magnetization is observed in comparison with the as-quenched ribbon meanwhile the exchange bias effect is enhanced.
The fabrication and the study of the magnetic properties of CoCrPt/Ti nanostructures produced by ... more The fabrication and the study of the magnetic properties of CoCrPt/Ti nanostructures produced by sputtering onto ordered polymer templates are reported here. Samples exhibit a significant outof-plane component of the magnetization higher than for planar films, and it is stronger for the thicker CoCrPt films, and for nanostructured films with the shorter period ordering. The shape of the polymeric templates plays an important role for the determination of magnetic easy-axis. Magnetic Force Microscopy images of the samples show a single magnetic domain structure with high outof-plane anisotropy for the samples with longer ordering (480 nm period).
The magnetic properties of radially-oriented Co, Ni, and CoNi alloy nanowires synthesized by puls... more The magnetic properties of radially-oriented Co, Ni, and CoNi alloy nanowires synthesized by pulsed electrodeposition into porous alumina structures are measured and compared with those of similar nanowires grown in a planar geometry. The alloy composition affects the anisotropy axis direction, which is determined by the balance between the magnetocrystalline and shape anisotropies, lying transverse to the nanowires for Co samples and along the nanowire axis for Ni. Monte Carlo simulations were performed to model the magnetic hysteresis of the radiallyoriented and planar geometry nanowires using an approach based on a conical distribution of anisotropies. The model provides an excellent fit compared with experimental hysteresis loops.
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