Amorphous Finemet films for visualization of inhomogeneous magnetic fields

This paper shows that amorphous Finemet films can be used as a medium for visualization and topography of inhomogeneous magnetic fields. The intensity of magnetooptical images obtained in the geometry of the polar magneto-optical Kerr effect is proportional to the normal component of the inhomogeneous magnetic field. This allows us to construct two-dimensional topograms of the normal component of the magnetic field. The images observed in the geometry of the longitudinal magneto-optical Kerr effect carry information about the planar component of the field. The vector field of the plane component has singular points that are displayed by magneto-optical images. Applying an external homogeneous field leads to the appearance of new singular points and their motion. At special points, the plane component of the field is equal to the value of the external field. This allows you to display a planar component by recording the coordinates of specific points. © Published under licence by IOP Publishing Ltd.Ministry of Science and Higher Education of the Russian Federation: 3.6121.2017/8.9The research was carried out within the state assignment of The Ministry of Science and Higher Education of the Russian Federation (project 3.6121.2017/8.9)

Magnetic properties of GdCo-Al2O3 composite films

The purpose of this work was to synthesize and study magnetic properties of composite films consisting of Gd-Co ferrimagnetic system and Al2O3 dielectric matrix. GdCo-Al2O3 films of different composition were synthesized by magnetron co-sputtering of Gd, Co, and Al2O3 targets in an Ar atmosphere. Investigation of magnetic properties was carried out using a vibrating sample magnetometer in the temperature range from 10 to 300 K. The obtained results showed that in the composite system with a volume of dielectric material exceeding 50% a superparamagnetic state is realized, indicating granular microstructure. In this case, the granules show signs of ferrimagnetic ordering. © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 18-72-10044This work was financially supported by the Russian Science Foundation in the framework of research project No. 18-72-10044

Annealing dependence of exchange bias in Fe20Ni80/NixMn100-x thin films

This work has been supported by the Ministry of Education and Science of the Russian Federation, project RFMEFI57815X0125

Nanocrystallization in FINEMET-type Fe73.5Nb3Cu1Si13.5B9 and Fe72.5Nb1.5Mo2Cu1.1Si14.2B8.7 thin films

A growing variety of microelectronic devices and magnetic field sensors as well as a trend of miniaturization demands the development of low-dimensional magnetic materials and nanostructures. Among them, soft magnetic thin films of Finemet alloys are appropriate materials for sensor and actuator devices. Therefore, one of the important directions of the research is the optimization of thin film magnetic properties. In this study, the structural transformations of the Fe73.5Nb3Cu1Si13.5B9 and Fe72.5Nb1.5Mo2Cu1.1Si14.2B8.7 films of 100, 150 and 200 nm thicknesses were comparatively analyzed together with their magnetic properties and magnetic anisotropy. The thin films were prepared using the ion-plasma sputtering technique. The crystallization process was studied by certified X-ray diffraction (XRD) methods. The kinetics of crystallization was observed due to the temperature X-ray diffraction (TDX) analysis. Magnetic properties of the films were studied by the magneto-optical Kerr microscopy. Based on the TDX data the delay of the onset crystallization of the films with its thickness decreasing was shown. Furthermore, the onset crystallization of the 150 and 200 nm films began at the temperature of about 400-420 °C showing rapid grain growth up to the size of 16-20 nm. The best magnetic properties of the films were formed after crystallization after the heat treatment at 350-400 °C when the stress relaxation took place. © 2020 by the authors.KK-2018/00099Ministry of Education and Science of the Russian Federation, Minobrnauka: 3.6121.2017/8.9Funding: The XRD study was funded by ACTIMAT (KK-2018/00099, Elkartek program). The magnetic properties study was supported by the Ministry of Education and Science of the Russian Federation in the framework of state tasks No. 3.6121.2017/8.9

Permalloy-based magnetic nanostruсtures for magnetoimpedance pressure sensors

The work was supported by the Ministry of Education and Science of Russia, project RFMEFI57815X0125

Effect of temperature on the exchange bias in FeMn/X/Fe20Ni80 (X = Ta, Gd) films

The influence of temperature on the exchange bias in the Fe50Mn50/X/Fe20Ni80 (X = Ta, Gd) films was investigated. It is shown that in the film structures without a spacer between FeMn and permalloy layers, the temperature dependence of the value of the exchange bias field is non-monotonous. The introduction of an ultrathin spacer leads not only to a change in the magnitude of the interlayer exchange coupling, but also to a change in the behavior of its temperature dependence. © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 18-72-10044The research work has been financially supported by the RSF grant, project no. 18-72-10044. The authors would also like to thank M.E. Moskalev for obtaining X-ray diffraction pattern of the film samples

Thin film based magnetoimpedance sensor for magnetic needle position indentification

The reported study was funded by RFBR according to the research project № 18-32-00094

Partial Structural transformation of NiMn in Exchange biased Fe20Ni80/Ni30Mn70/Fe20Ni80 thin films

Features of crystal structure and exchange bias of annealed Fe20Ni80/Ni30Mn70/Fe20Ni80 thin films are investigated. Temperature dependences of hysteresis loops reveal that for a sample with a thicker FeNi bottom layer a blocking temperature exceeds a Néel temperature of A1 -NiMn by 20K, while for a sample with a thinner FeNi bottom layer a blocking tem-perature is larger than the Néel temperature by 140K. An explanation of the influence of the bottom FeNi layer on the phase transformation in NiMn is proposed.This work was financially supported by the Russian Science Foundation (RSF), project No. 18-72-10044