P. A. Savin

Fe20Ni80/Fe50Mn50 film magnetoresistive medium

The influence of several physico-technological factors on the microstructure and the magnetic and magnetoresistive properties of film structures based on Fe20Ni80/Fe50Mn50 bilayers with exchange (magnetic) bias is investigated. The dependences of the magnetic bias, coercive force, and anisotropic magnetoresistance on the deposition sequence and thickness of layers in the structures, substrate temperature, annealing temperature, and measurement temperature are determined for films obtained by magnetron sputtering, including with a high-frequency electric bias applied to the substrate. It is shown that the film SiO2/Ta(5)/Fe20Ni80(5)/Fe50Mn50(20)/Fe20Ni80(40)/Ta(5) structure offers an optimal combination of properties as a magnetoresistive medium with internal magnetic bias. Testing data for magnetic sensors made of this material by optical lithography are presented.

Tailoring the Exchange Bias in FeNi/FeMn Bilayers by Heat Treatment and FeMn Surface Oxidation

The FeNi(30 nm)/FeMn(20 nm) bilayers were deposited by magnetron sputtering at room temperature onto glass substrates in a magnetic field. Afterward, they were subjected to heat treatments at temperatures from 50 °C to 400 °C in vacuum or in a gas mixture containing oxygen. The as-deposited FeNi/FeMn bilayers presented an exchange bias field Hex = 30 Oe, a coercivity Hc ≈ 3 Oe, and a blocking temperature Tb ≈ 140 °C. An increase of the annealing temperature results in a monotonous decrease of Hex for temperatures up to 200 °C. For higher annealing temperatures, Hex remains almost constant. Hc sharply increases in the range from 200 °C to 300 °C, and finally decreases dramatically upon annealing>300 °C. Preferential surface oxidation of Mn during heat treatment in a gas mixture results in the formation of the ferromagnetic α-Fe(Mn) phase and leads to the change of the magnetic moment of the samples. The adjustment of temperature and annealing time in a gas mixture allows us to increase the switching field value of exchange biased FeNi/FeMn bilayers.

Spin-valve magnetoresistive structures based on Co/Tb multilayer films

The effect of the layer thickness on the magnetic properties of {Co/Tb}n, {Co/Tb}n/Co, and {Co/Tb}n/Co/Cu/Co multilayer films is studied. The dependence of the hysteresis and magnetoresistive properties of {Co(1 nm)/Tb(1 nm)}n/Co(5 nm)/Cu(LCu)/Co(5 nm) structures on the thickness of the {Co/Tb}n layer and copper spacing are obtained. The feasibility of spin-valve structures based on {Co/Tb}n multilayer films with in-plane anisotropy is demonstrated.

Effect of Substrate RF-Bias on Exchange Coupling in Fe20Ni80/Fe50Mn50 Films

The effect of physical and technological factors on the effectiveness of the exchange coupling in two-layer film structures such as Fe20Ni80/Fe50Mn50 has been investigated. The dependences of the coercive force and the exchange bias field of permalloy layer on presence of a buffer Ta layer and its thickness, the order of sputtering and the thickness of Fe20Ni80 and Fe50Mn50 layers, substrate temperature and the features of radio-frequency (RF) substrate bias during deposition were investigated. It has been found that the substrate RF bias improves homogeneity of microstructure and reduces the surface roughness of permalloy layer. This in turn increases the magnetic pinning of permalloy layer and creates the prerequisites for the practical application of layered structures with higher thickness of the ferromagnetic layers.

Effect of phase separation in an Fe20Ni80/Fe50Mn50 structure with exchange coupling

The effect of heat treatment and partial oxidation of an Fe50Mn50 layer on the structure and magnetic properties of exchange-coupled Fe20Ni80/Fe50Mn50 layers has been investigated. The behavior of the exchange-bias field and coercive force depending on the temperature of annealing upon heat treatment in a vacuum or in an oxygen-containing gas mixture has been studied. It has been shown that, by adjusting the parameters of annealing in the gas mixture, it is possible to increase the field of switching of the exchange-coupled Fe20Ni80/Fe50Mn50 layers.

Co/Cu/Co Pseudo Spin-Valve System Prepared by Magnetron Sputtering with Different Argon Pressure

Thin Co films were fabricated by DC magnetron sputtering. The effect of argon pressure on the microstructure, surface morphology and magnetic properties of the samples was systematically studied. It was found that with the increase of argon pressure, the sharpness of the crystalline texture of the samples declines, the roughness of film surfaces and the coercivity of the films increase. Based on these results, a Co/Cu/Co pseudo spin-valve system was designed and the corresponding structures were fabricated. The difference in coercivity of magnetic layers was obtained by deposition of the Co layers at different Ar pressures. Change of the resistance of this trilayer is induced at a moderate field by the spin rotation in the soft layer with lower coercivity.

Optimization of Functional Parameters of Magnetoresistive Fe 20 Ni 80 /Fe 50 Mn 50 /Fe 20 Ni 80 Films

In this paper, the effect of some technological and physical factors on properties of SiO₂/Ta/Fe₂₀Ni₈₀/Fe₅₀Mn₅₀ and SiO₂/Ta/Fe₂₀Ni₈₀/Fe₅₀Mn₅₀/Fe₂₀Ni₈₀/Ta films, having the anisotropic magnetoresistance (AMR) effect, was investigated. The purpose of this paper was to find the optimum conditions for realization of the peak magnetic biasing in thick (>30 nm) permalloy layers. Essential influence of the protective Ta layer on the achievement of the optimal combination of properties of multilayer AMR films with exchange coupling is shown. Dependences of the exchange bias field (H_ex) and maximum derivation of resistance with respect to magnetic field (dR/dH)_max on the thickness of functional permalloy layers are investigated. The preproduction prototypes of a sensor are produced and sensor transformation function is investigated.

Influence of Interlayer Interfaces on Exchange Coupling Efficiency in Multilayer Magnetoresistive Films With Fe 50 Mn 50 Layers

The role of preparation conditions and parameters of the layered structure on the magnetoresistive properties of Fe₂₀Ni₈₀/Fe₅₀Mn₅₀ and Fe₂₀Ni₈₀/Fe₅₀Mn₅₀/Fe₂₀Ni₈₀ films with exchange coupling have been investigated. It was found that relative position of the Fe₂₀Ni₈₀ and Fe₅₀Mn₅₀ layers as well as presence of the high frequency electric bias of the substrate during film deposition affect the efficiency of the exchange interaction. Dependences of the exchange bias field and anisotropic magnetoresistance on the heat treatment conditions for the films with different layered structures were analyzed.

Effect of technological conditions on the magnetic and magnetoresistive properties of Fe20Ni80/Fe50Mn50 films

The effect several physical and technological factors have on the magnetic and magnetoresistive properties of Fe20Ni80/Fe50Mn50 multilayers is studied. The best technological conditions for preparing films with high exchange bias fields (∼30 Oe) and high anisotropy of the magnetoresistive effect (∼2%) are determined.