PHYSICS OF MAGNETISM

The European Conference Physics of Magnetism 2014

PM'14 conference official photoDate: June 23-27, 2014

Poznan, Poland


Abstracts:

In last years, Ni-Mn-X Heusler alloys have attracted significant attention because of number of their functional properties. Ni-Mn-Ga glass-coated microwires (MWs) have a good prospects for new generation technical applications. We investigated magnetic and structural properties of the Ni-Mn-Ga MWs fabricated by Tailor-Ulitovsky method. MWs with total diameter of 54.6 and 24.7 µm and the diameter of metallic core of 26.7 and 8.3 µm, respectively, were obtained. Energy dispersive spectrometer (Oxford Instr. X-Act) was used to detect composition of the metallic core of as-cast and annealed MWs. Magnetic moment versus temperature (-196-77 C) measurements and hysteresis loops were obtained by VSM (Lakeshore 7400 system). X-Ray diffraction (using Bruker D8 Discover in temperature range of -100-350 C) and magnetic temperature measurements reveal martensitic transition in the samples near the room temperature.

Several topics of photonic are targeted on the enhancement of magneto-optical response in nanostructures. One of such approaches is creating magnetoplasmonic crystals (MPC) based on digital discs with ferromagnetic film. It is necessary to investigatein-plane anisotropy of MPC sandin fluence of ferromagnetic layer to improve the quality factor of plasmons. MPCs based on Fe and Ni were investigated using VSM by LakeShore and a step-like behavior of hysteresis loops in case of transverse plasmon propagation way was observed. Measurements along the plasmon propagation way showed near-rectangular hysteresis loops typical for Ni-based thin films. In-plane anisotropy was found in Ni thin films on Si/SiO2 substrate, too. All Fe structures had isotropic in-plane magnetic properties.

In-plane anisotropy for Ni onSi/SiO2 can be explained by magnetostriction properties of Ni. For MPCs it can be explained as a result of interaction between different factions of Ni that partly covered sides of the substrate battlements

Amorphous ferromagnetic glass coated microwires (MWs) are one of the most perspective materials for coding system and memory applications. For successful implementation of these devices it is necessary to control MWs magnetic properties and domain wall dynamics. In this work we investigated the effect of annealing under tensile applied stress on magnetic properties of amorphous MWs with compositions of Co68,6B14,8Si10Mn6,6, Co68,7Fe4Ni1B13Si11Mo2,3 and Fe3,85Co67,05Ni1,44B11,53Si14,47Mo1,66. Samples of MWs were annealed at temperatures of 300-400 C during different times up to 90 min with different applied stresses up to 300 Pa. We observed changing of the magnetic properties depending on all parameters of annealing. Some conditions of annealing lead to appear of bistability and possibility to observe the domain wall movement with high velocity. Besides, it was shown that MWs with acquired bistability can be more useful for applications than originally bistable.

The nearly equiatomic Fe–Rh alloys when heated without an external influences to critical temperature suffer the first-order antiferromagnetic–ferromagnetic transition. The reverse transition takes place at lower temperature. The width of thermal hysteresis can be varied by the changing of alloy’s chemical content, preparation technique of the samples, heat- and mechanical treatment in wide range of temperatures. To decrease the hysteresis – it is importante for technical applications. More over, each subsequent measurement leads to changing of the antiferromagnetic–ferromagnetic transition temperature. This research work was aimed to find the composition of equiatomic Fe–Rh alloy with extremly narrow thermal hysteresis and repeatable results. Vibrating sample magnetometer by Lake Shore was used for measurements of magnetic moment versus temperature in range of 100-950 K.

Magnetic properties of ferromagnetic/antiferromagnetic thin-films structures for spinvalve applications have been studied. Multilayer structures of Ta/Co/IrMn/Ta and Ta/FeNi/IrMn/Ta were deposited on Si substrate at room temperature by DC magnetron sputtering. Thickness of the antiferromagnetic layer changed from 2 to 60 nm. Uniform forming magnetic field of 420 Oe was applied parallel to the sample’s plane during the deposition. The magnetic properties of these structures were obtained from ferromagnetic resonance and vibrating sample magnetometry measurements. Both the coercive force and the exchange bias field were found to be non-monotonic functions of the antiferromagnetic layer thickness. To achieve the maximum effect of the exchange bias the optimal thicknesses were found for each system. More over, it was found the alternative sequence of the deposition (antiferromagnetic layer on the top or below the ferromagnetic layer) leads to dramatic changes of the magnetic properties of bilayer structures.

To operate with objects of micro and nanosizes it is necessary to have small “instruments”. For this purpose we can use a microactuator, made of a partially covered magnetically biphase microwire, which can be controlled by means of a magnetic field. In this work we have studied, analyzed and compared the magnetic properties of two series of fully covered magnetically biphase microwires with different thickness of the hard or soft shell, in order to understand the magnetostatic interaction between the shell (CoNi- or FeNi- based) and the core (Fe- or FeCo-based glass-coated microwires). The magnetic properties were analyzed as a function of temperature in the range from 295 K to 1200 K using a Vibrating Sample Magnetometer (Lake Shore). The magnetic properties of samples varied with the thickness of the shell. Analysis of the magnetization process of each phases with measuring temperature has been performed.


“The European Conference Physics of magnetism 2014 (PM’14)”

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