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.
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.
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
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.
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.
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.
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
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.
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