Exchange biased FeNi/FeMn bilayers with coercivity and switching field enhanced by FeMn surface oxidation

Abstract

FeNi/FeMn bilayers were grown in a magnetic field and subjected to heat treatments at temperatures of 50 to 350 °C in vacuum or in a gas mixture containing oxygen. In the as-deposited state, the hysteresis loop of 30 nm FeNi layer was shifted. Low temperature annealing leads to a decrease of the exchange bias field. Heat treatments at higher temperatures in gas mixture result in partial oxidation of 20 nm thick FeMn layer leading to a nonlinear dependence of coercivity and a switching field of FeNi layer on annealing temperature. The maximum of coercivity and switching field were observed after annealing at 300 °C.

Exchange bias in FeNi/FeMn/FeNi multilayers

“…This causes the formation of two exchange bias subsystems in a single bilayer. At low temperatures, these areas with different exchange bias shift the loop in opposite directions [22,[35][36][37]. The same result was obtained, when the FM was first saturated at 200°C by applying the positive field and then was cooled at H FC = À1.2 Oe applied along the EMA (Fig.…”

“…Permalloy was sputtered using a Fe 19 Ni 81 target and an antiferromagnetic layer using a Fe 50 Mn 50 target. The samples were grown on a Ta(5 nm) underlayer to promote (1 1 1) texture in FeNi and FeMn layers and capped with a Ta (10 nm) layer to prevent oxidation [35]. The deposition rates were previously calibrated as 8 nm/min for FeNi layers, 5 nm/min for FeMn layers and 2 nm/min for Ta layers.…”

Optimization of Functional Parameters of Magnetoresistive Fe₂₀Ni₈₀/Fe₅₀Mn₅₀/Fe₂₀Ni₈₀ Films

“…Both types of samples were obtained at a room temperature and not annealed. Measurements carried out on X-ray diffractometer [3] have shown affinity of structure parameters of both samples types ( Fig. 1).…”

Influence of Interlayer Interfaces on Exchange Coupling Efficiency in Multilayer Magnetoresistive Films With Fe₅₀Mn₅₀ Layers

“…Such a technique should increase the average size of the crystallites, at least up to the value exceeding the mean free path of electrons in the material. At the same time, the heat treatment may lead to very large changes in the interlayer interaction of the Fe 20 Ni 80 /Fe 50 Mn 50 bilayers [11]. Two modes of thermal influence were proposed.…”

“…The possible reason for such feature is inhomogeneous chemical composition across the thickness of Fe 50 Mn 50 layer that has been indicated in [11] and [12]. To estimate the possibility of such a mechanism, the auxiliary experiment was performed on Fe 50 Mn 50 12 nm thick samples deposited onto Si single-crystal substrates.…”