The possibility of electrical control of the interlayer exchange interaction in CoFeB/MgO/CoFeB tunnel junctions exhibiting magnetoresistance of ~200% is studied. It is shown that the increase in the applied voltage from 50 mV to 1.25 V leads to a shift of the magnetization curve of the free layer by 10 Oe at a current density of ~10(3)A/cm(2). The discovered effect can be used in the development of energy-efficient random access memory.

We have developed technology for manufacturing chains of CoFe/Al 2 O 3 /NiFe tunnel magnetoresistive (TMR) elements with pinning on the IrMn antiferromagnetic layer. We have studied the dependence of the shape of magnetoresistance curves on the geometric parameters of laterally bounded TMR contacts, as well as on the mutual orientation of the external magnetic field and the axis of unidirectional anisotropy of the pinned CoFe layer. The chain resistance ranges from several tens of kiloohms to hundreds of megaohms depending on the thickness of the tunnel-transparent dielectric layer with a magnetoresistive effect of 10–15%. The developed technology can be used in manufacturing tunneling magnetic field sensors.

The temperature dependence of the linear electrodynamic response of thin-film superconductor (MoN)–normal metal (Al) hybrid structures with a high conductivity ratio in the normal state has been theoretically and experimentally investigated. Low-frequency measurements of the coefficient of mutual induction of two coils with a sample placed between them indicate an increase in the magnetic screening of the superconductor–normal metal (SN) structures with an increase in the Al layer thickness dAl near liquid-helium temperatures. Measurements of the frequency shift δf of a microwave dielectric resonator, brought into contact with the sample, as a function of temperature and dAl showed that (i) the character of the dependence δf(T) depends strongly on dAl and (ii) the resonance frequency shift of SN structures at temperatures close to the critical temperature Tc is not described by dependence const/(1 – T/Tc), which is typical of thin superconducting films. Numerical calculations performed within the Usadel model well describe the observed effects. Thus, these anomalies of the electrodynamic properties of SN structures can be explained by the presence of a minigap in the spectrum of quasiparticles due to the proximity effect in a normal-metal layer, which depends on dAl, and by the high conductivity of the Al layer.

Temperature dependence of linear electrodynamic response of thin-film hybrid structures superconductor (MoN) — normal metal (Al) with large ratio of normal-state conductivities was studied theoretically and experimentally. Low-frequency measurements of the mutual inductance of two coils with a sample placed between them indicated an increase in magnetic screening ability of the superconductor – normal metal (SN) hybrid structures at liquid helium temperatures as $d_Al$ increases, where $d_Al$ is the thickness of the Al layer. Measurements of the frequency shift $\delta f$ of the microwave dielectric resonator, which was in contact with the SN samples as a function of temperature and $d_Al$ demonstrated that (i) type of the $\delta f(T)$ dependence depends significantly on $d_Al$ and (ii) the shift of resonant frequency of the SN structures at temperatures close to the critical temperature Tc cannot be approximated by a functional dependence $const/(1–T/T_c)$, which is typical for thin superconducting films. Numerical calculations performed within the Usadel model describe the observed effects quite well. Thus, the mentioned anomalies of the electrodynamic properties of the SN hybrid structures can be explained by an appearance of a mini-gap in the spectrum of quasi-particle excitation caused by the proximity effect in the normal metal layer, which depends on $d_Al$ as well as by the high conductivity of the Al layer.

AbstractThe effect of strains on ferromagnetic particles has been studied. Arrays of Ni microparticles of different shapes on glass substrates have been fabricated. The magnetic state of the fabricated particles as a function of the degree of glass substrate bending has been investigated. It has been established that the ground state of unbent particles is vortex. It is shown that the substrate bending leads to the transition from the vortex to quasi-homogeneous state.

Using the near-field microwave microscopy method, the temperature dependence of third harmonics power P3ω(T) of the MoN/Al superconductor–normal metal structures with the proximity effect is studied. The presence of a secondary (low-temperature) maximum and zeroings is detected in the P3ω(T) dependence of the MoN/Al structure, which disappear upon applying a weak magnetic field perpendicular to the plane of the structure.

We experimentally study the interlayer interaction in a magnetic multilayer system ferromagnet/insulator/ferromagnet with different spacer thickness. The sign and the magnitude of the interaction can be deduced from the ferromagnetic resonance (FMR) peak shape rather than the FMR peak shift. The proposed technique allows studying the interlayer interaction using a single sample (without a reference sample for comparison).

The effect of strains on ferromagnetic particles has been studied. Arrays of Ni microparticles of different shapes on glass substrates have been fabricated. The magnetic state of the fabricated particles as a function of the degree of glass substrate bending has been investigated. It has been established that the ground state of unbent particles is vortex. It is shown that the substrate bending leads to the transition from the vortex to quasi-homogeneous state.

Using the method of near-field microwave microscopy, we investigated the temperature dependence of the third harmonic power P3ω (T) of superconductor – normal metal MoN / Al structures with proximity effect. The presence of an additional (low-temperature) maximum and vanishing in the dependence P3ω (T) for the MoN / Al structure, which disappear when a weak perpendicular magnetic field is applied.

The technology of fabricating of chains of tunnel magnetoresistive (TMR) elements based on CoFe/Al2O3/NiFe nanostructures with pinning on the antiferromagnetic IrMn layer has been developed. The dependence of the magnetoresistance curves on the geometrical parameters of the laterally bounded TMR contacts, as well as on the mutual orientation of the external magnetic field and the axis of the unidirectional anisotropy of the fixed CoFe layer has been investigated. The resistance of the chains has been varied from several tens of kΩ to hundreds of MΩ, depending on the thickness of the tunnel dielectric layer. The magnitude of the magnetoresistive effect has been about 10–15%. The suggested technology can be used to make tunnel magnetic field sensors

We present the results of creating a cooled microbolometer based on the cermet films of the silicon and chromium mixture. This material is used for manufacturing the freely hanging high-resistive microbolometers for the first time. The details of fabricating such microbolometers and the prospects for using cermet films to construct microbolometers are discussed. The first estimates of sensitivity of the fabricated microbolometers are given.

In this paper the results of the investigation of Si-Cr x resistive cermet films, which are promising for the development of broadband microbolometers of the microwave range, are presented. A model of the conductivity of cermet films based on the theory of transport in granular metals and diluted semiconductors is proposed.

Mirror polarizers for thermal neutrons are proposed and developed. In contrast to the widespread practice where mirrors are constantly in an external magnetizing field of more than 1 kOe, we have solved the problem of the efficient operation of a polarizer when a weak magnetic field of about 50 Oe is applied perpendicular to its surface.

Linear and nonlinear optical properties of a thin planar CoFe/Al2O3/CoFe structure for different angles of incidence of the fundamental radiation are studied by means of the magneto-optical Kerr effect and magnetization-induced second-harmonic generation (SHG). The composition of this multilayered structure supports the appearance of the antiferromagnetic state, which leads to nonreciprocal optical effects and is discussed in terms of the magnetic toroid moment. We show that in accordance with the phenomenological description, SHG magnetic hysteresis loops for a linearly polarized pump beam are determined by linear in magnetization M components of the SHG polarization, while for a circularly polarized pump such a description necessarily involves both linear and quadratic in M components of the nonlinear polarization. Symmetry analysis of the magnetization-induced SHG supports the differences between the cases of linear and circular polarization of the incident radiation observed in the experiment, as well as a partial suppression of first in magnetization SHG contributions. Relative values of the linear and quadratic in magnetization components of the SHG polarization are estimated for the trilayer structure and for a reference homogeneous ferromagnetic film. (C) 2015 Optical Society of America

A possibility of fabrication of a microelectromechanical tunneling sensor without a feedback loop is demonstrated. The tunneling gap of less than 10 nm shows a long-term stability at room conditions. The sensor can be used for construction of an accelerometer in which the linear acceleration causes mutual displacements of mobile microelectrodes. Acceleration can be detected due to a strong dependence of the tunneling current on interelectrode gap. The sensor is fabricated on a silicon-on-insulator (SoI) wafer in the planar technology. Experiments have shown the accelerometer resolution to be 2.221 g/Hz 1/2 at frequencies up to 3.17 kHz. The frequency of the first mechanical vibration mode of the sensor was estimated at a few MHz. By lowering this frequency through an increase in the proof mass, it is possible to largely upgrade the resolution of the accelerometer.