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An FeRh thin film of 33 nm thickness grown by molecular beam epitaxy (MBE) has been investigated with respect to its temperature dependent magnetic properties by means of ferromagnetic resonance (FMR). Within the ferromagnetic regime, that is at temperatures above the antiferromagnetic-to-ferromagnetic phase transition, the resonance field decreases with decreasing temperature reflecting an increasing magnetization. Within the temperature regime of the phase transition, the resonance field behaves non-monotonically, that is it suddenly increases with decreasing temperature. The observed asymmetric shape of the FMR absorption line is discussed with respect to a possible small magnetic inhomogeneity of the film coupled to the main ferromagnetic volume of B2 ordered, equiatomic FeRh.

AdetailedstudyofthemagneticandtransportpropertiesofSi1−xMnx (x ≈ 0.35)filmsispresented.Weobserve the anomalous Hall effect in these films up to room temperature. The results of the magnetic measurements and the anomalous Hall effect data are consistent and demonstrate the existence of long-range ferromagnetic order in the systems under investigation. A correlation of the anomalous Hall effect and the magnetic properties of the samples with their conductivity and substrate type is shown. A theoretical model based on the idea of a two-phase magnetic material, in which molecular clusters with localized magnetic moments are embedded in the matrix of a weak itinerant ferromagnet, is discussed and used to explain experimental results. The long-range ferromagnetic order at high temperatures is mainly due to the Stoner enhancement of the exchange coupling between clusters through thermal spin fluctuations (“paramagnons”) in the matrix. Theoretical predictions do not contradict experimental data when model parameters of a plausible order of magnitude are used.

Magnetic elastomers (MEs) based on a silicone matrix and magnetically hard NdFeB particles have been synthesized and their magnetic and viscoelastic properties have been studied depending on the size and concentration of magnetic particles and the magnetizing field. It has been shown that magnetic particles can rotate in soft polymer matrix under applied magnetic field, this fact leading to some features in both magnetic and viscoelastic properties. In the maximum magnetic field used magnetization of MEs with smaller particles is larger while the coercivity is smaller due to higher mobility of the particles within the polymer matrix. Viscoelastic behavior is characterized by long relaxation times due to restructuring of the magnetic filler under the influence of an applied mechanical force and magnetic interactions. The storage and loss moduli of magnetically hard elastomers grow significantly with magnetizing field. The magnetic response of the magnetized samples depends on the mutual orientation of the external magnetic field and the internal sample magnetization. Due to the particle rotation within the polymer matrix, the loss factor increases abruptly when the magnetic field is turned on in the opposite direction to the sample magnetization, further decreasing with time. Moduli versus field dependences have minimum at non-zero field and are characterized by a high asymmetry with respect to the field direction.

The effect of a uniform magnetic field on the permittivity of magnetorheological elastomers (MREs) is studied. MREs were synthesized on the basis of silicone rubber and magnetic fillers of various chemical nature (Fe, NdFeB and Fe3O4) and particle sizes. The value of permittivity was obtained from the measurements of the capacity of a plane capacitor with MRE samples. A strong increase of the permittivity (magnetodielectric effect) was observed when the applied field was perpendicular to the capacitor plates. The value of the magnetodielectric effect was found to be strongly dependent on the type of magnetic filler as well as on the size and concentration of magnetic particles within MRE composites. The highest magnetic response reaching 150% was observed for the MRE based on a magnetically hard NdFeB filler. A simple model explaining physical reasons for the magnetodielectric effect in a MRE is proposed. The developed MRE with a strong magnetodielectric effect is very promising for a wide range of applications, in particular, as magnetic field sensors and actuators.

The structure of an epitaxial thin film of cobalt-doped hexagonal LuFeO3 was studied by aberration-corrected high-resolution scanning transmission electron microscopy. The distribution maps of the chemical elements in the film were obtained using atomically resolved energy-dispersive X-ray spectroscopy. The study showed that cobalt ions have a strong tendency towards forming double layers of (Fe/Co)O-2.5 between the Lu-O layers in a hexagonal structure. A significantly smaller amount of cobalt is found in single layers of FeO1.5, suggesting the presence of a trigonal-bipyramidal coordination of cobalt. The hexagonal LuFeO3 structure contains numerous reconstructed stacking faults that represent intergrown structural fragments of LuFe2 - xCoxO4. Magnetization measurements revealed a decrease in the magnetic transition temperature of the LuFe0.7Co0.3O3 thin film compared to those of the parent hexagonal LuFeO3 and LuFe2 - xCoxO4 forms.

Hexagonal orthoferrites of rare earths RFeO3 (R = Lu, Er-Tb) were grown epitaxially on (111)ZrO2(Y2O3) substrates using metal-organic chemical vapour deposition. Temperature and field dependences of magnetization were measured and analyzed for all samples and revealed weak ferromagnetic behavior below T = 120–140 K. The difference in electronic structure along with a distinct similarity in the crystal structure of hexagonal manganites RMnO3 and hexagonal orthoferrites RFeO3 are brought into focus in order to explain the results. Hexagonal orthoferrites are regarded as a promising family of multiferroics.

InMnAs layers were fabricated by pulsed laser ablation of solid targets (Mn and InAs) in flow of hydrogen and arsine. The InMnAs layers with thickness ranging from 130 to 270 nm were deposited on semi-insulating GaAs (100) substrates at 320°C. The Mn quantity was controlled by changing ratio of sputtering time of Mn and InAs targets. The X-ray diffraction measurements identified the InMnAs as mosaic monocrystal with MnAs phase texture inclusions. Room temperature ferromagnetism of these InMnAs layers is evident from magnetometry and magneto-optical measurements. In addition, the InMnAs layers show anomalous Hall effect with the hysteresis loop and saturation magnetic field HS ≈ 2500 Oe at temperatures up to 300K depending on the Mn content. The Curie temperature higher than 300K allows using these magnetic semiconductor layers as a source of spin polarized carriers in room temperature spintronic devices.