Effect of Cr spacer on structural and magnetic properties of Fe/Gd multilayers

In this work we analyse the role of a thin Cr spacer between Fe and Gd layers on structure and magnetic properties of a [Fe(35A)/Cr(tCr)/Gd(50A)/Cr(tCr)]x12 superlattice. Samples without the Cr spacer (tCr=0) and with a thin tCr=4A are investigated using X-ray diffraction, polarized neutron and resonance X-ray magnetic reflectometry, SQUID magnetometery, magneto-optical Kerr effect and ferromagnetic resonance techniques. Magnetic properties are studied experimentally in a wide temperature range 4-300K and analysed theoretically using numerical simulation on the basis of the mean-field model. We show that a reasonable agreement with the experimental data can be obtained considering temperature dependence of the effective field parameter in gadolinium layers. The analysis of the experimental data shows that besides a strong reduction of the antiferromagnetic coupling between Fe and Gd, the introduction of Cr spacers into Fe/Gd superlattice leads to modification of both structural and magnetic characteristics of the ferromagnetic layers

Magnetic ordering in Fe/X/Gd (X=Cr, Pd) superlattices

We have studied the influence Cr and Pd spacers on structure and magnetic ordering in Fe/Gd superlattices. The insertion of Cr and Pd spacers in Fe/Gd has been found to cause structural changes in Gd layers. In particular, an additional fcc Gd phase appears in Fe/Cr/Gd along with the main hcp Gd phase, while there is amorphous Gd structure in Fe/Pd/Gd. By combining SQUID magnetometry and polarized neutron reflectometry we have shown that interlayer Fe-Gd exchange coupling through Pd spacers is much stronger than through Cr one. © Published under licence by IOP Publishing Ltd.Russian Foundation for Basic Research, RFBR: 18-32-00197, 19-02-00674Ministry of Education and Science of the Russian Federation, Minobrnauka: AAAA-A18-118020290104-2The results were obtained within the state assignment of Ministry of Education and Science of Russia (subject “Spin” AAAA-A18-118020290104-2) and in part supported by the Russian Foundation for Basic Research (projects Nos. 18-32-00197 and 19-02-00674)

Magnetoresistive properties of exchange biased spin valve caused by helical magnetic ordering in dysprosium layer

Spin valves containing CoFe/Dy/CoFe nanostructure as a pinned layer were prepared by magnetron sputtering. Investigations of microstructure and magnetoresistive properties were performed. The magnetoresistive properties of the spin valve were used as the instrument to study the changes in magnetic state of the dysprosium layer. The existence of noncollinear magnetic ordering in dysprosium polycrystalline nanolayer was observed. The angle between the magnetic moments in a top and bottom part of the dysprosium layer was estimated. © Published under licence by IOP Publishing Ltd

Magnetization and ferromagnetic resonance in a Fe/Gd multilayer: Experiment and modelling

Static and dynamic magnetic properties of a [Fe(35 Å<rf)/Gd(50 Å)]12 superlattice are investigated experimentally in the temperature range 5-295 K using SQUID magnetometery and the ferromagnetic resonance (FMR) technique at frequencies 7-38 GHz. The obtained magnetization curves and FMR spectra are analysed theoretically using numerical simulation on the basis of the effective field model. At every given temperature, both static and resonance experimental data can be approximated well within the proposed model. However, a considerable temperature dependence of the effective field parameter in gadolinium layers has to be taken into account to achieve reasonable agreement with the experimental data in the entire temperature range studied. To describe the peculiarities of experimental FMR spectra, a non-local diffusion-type absorption term in Landau-Lifshitz equations is considered in addition to the Gilbert damping term. Possible reasons for the observed effects are discussed. © 2017 IOP Publishing Ltd

Microstructure and magnetoresistance of Co90Fe10/Cu and Co65Fe26Ni9/Cu multilayers

Investigations of the microstructure, magnetic and magnetotransport properties of the optimized [Co90Fe10/Cu]n and [Co65Fe26Ni9/Cu] n multilayers with n = 32 prepared by magnetron sputtering are performed. These nanostructures exhibit the magnetoresistance values 83 % and 36 % at room temperature, respectively. The article presents the results of the influence of Co65Fe26Ni9 alloy on the magnetoresistance values and crystal structure of multilayers. In the periodic part of the nanostructure [Co65Fe26Ni9/Cu] n based on CoFeNi ternary alloy, besides fcc the formation of a bcc phase in the continuous boundaries around crystallites is found. © Published under licence by IOP Publishing Ltd

Spin valve based sensor elements for full Wheatstone bridge

Present work deals with methods for creating opposite pinning directions in micro-objects based on a spin valve by one thermomagnetic treatment. The methods are based on the thermomagnetic treatment in spin-flop state of synthetic antiferromagnet. We use splitting the magnetic structure in spin-flop state of synthetic antiferromagnet to form opposite pinning directions in different micro-objects by one thermomagnetic treatment. The positive characteristic (dR/dH) was obtained in the two sensor elements of the full Wheatstone bridge, and the negative characteristic (dR/dH) in the other two elements. © Published under licence by IOP Publishing Ltd.Russian Foundation for Basic Research, RFBR: 19-02-0005718-10-2-37The research was carried out within the state assignment of Minobrnauki of Russia (theme “Alloys” АААА-А19-119070890020-3 and “Magnet” АААА-А18-118020290129-5), supported in part by RFBR (project No. 19-02-00057) and UD RAS (No. 18-10-2-37)

Neutron reflectometry studies of Gd/Nb and Cu30Ni70/Nb superlattices

We performed a comparative study of magnetic proximity effects in [Gd(5nm)/Nb(25nm)]12 and [Cu30Ni70(6nm)/Nb(27nm)]12 superlattices of S/F type by means of transport measurements and neutron scattering. Transport measurements have shown that Gd/Nb and CuNi/Nb superlattices shows 3D and 2D type of superconductivity respectively. In the case of proximity coupled Gd/Nb superconductor the effective thickness of the superconducting region, 300nm is enough to expel significant amount of applied magnetic field which was detected by neutron scattering. In decoupled CuNi/Nb superlattice thickness of every superconducting layer is only 27nm which is not enough to expel applied magnetic field. Our study shows how neutron reflectometry can be applied to study proximity coupling in superconducting/ferromagnet heterostructures

Ant-aphid relations in Costa Rica, Central America (Hymenoptera: Formicidae; Hemiptera: Aphididae)

We present the first catalogue of ant-aphid associations (Hymenoptera: Formicidae / Hemiptera: Aphididae) of Costa Rica. 29 species of ants and 18 species of aphids establish 48 relationships. Those interactions seem not to be rare in Costa Rica

Influence of Dimensional Effects on the Curie Temperature of Dy and Ho Thin Films

Abstract: The role of size effects in the formation of the magnetic structure of Dy and Ho thin films in absence of epitaxial strain is studied in this work. It was found that, for Dy in the temperature range between the Néel temperature and the Curie temperature of bulk Dy and, for Ho, in the temperature range between the Néel temperature and the temperature of phase transition into the conic phase, the temperature dependences of the period of magnetic helicoid in the bulk and film metals are similar. The character of the transition into the ferromagnetic phase in the Dy films changes at lower temperatures, and the transition into the commensurable conic phase in the Ho films is suppressed. This is explained exclusively by the influence of dimensional effects. © 2021, Pleiades Publishing, Ltd.Synthesis of samples and magnetometric measurements were performed at the Center of the Collaborative Access, Institute of Metal Physics, Ural Branch, Russian Academy of Sciences. Experimental data obtained with the REMUR reflectometer were transformed from the instrumental coordinate system into the reciprocal space coordinate system using Överlåtaren software []. This study was supported by the Russian Foundation for Basic Research, project no. 19-32-90007

PREDICTION OF MAGNETOTRANSPORT PROPERTIES OF SUPERLATTICES BASED ON MACHINE LEARNING METHODS

In the course of this work, a regression machine learning model was constructed based on a set of experimental data capable of predicting the magnetotransport properties of CoFeNi/Cu and CoFeNi/CuIn superlattices.Работа выполнена в рамках государственного задания МИНОБРНАУКИ России по темам «Спин» 122021000036-3 и «Магнит» 122021000034-9