Exchange anisotropy in polycrystalline FeNi∕FeMn films with hysteresis loop asymmetry

Abstract

The process of magnetization reversal of a FeNi(50Å)∕FeMn(50Å) polycrystalline film prepared in a magnetic field has been investigated at temperatures ranging from 25to300K. The external field was oriented in the film plane along the easy or difficult axis of the ferromagnetic layer. In the process of magnetization reversal of the film along the easy axis, strong asymmetry of the hysteresis loop is observed together with an exchange shift. As temperature decreases, the asymmetry becomes more pronounced and the shift increases. The field dependences of the magnetization of the film are symmetric and are not shifted when the external field is applied along the difficult axis. The magnetization reversal process is examined on the basis of a model that takes account of the appearance of high-order exchange anisotropy in polycrystalline films. It is shown that the observed strong asymmetry of the hysteresis loop is associated with the formation of a canted phase and the existence of a metastable state. As the film temperature decreases, the interval of fields where the canted phase can exist becomes wider as a result of an increase of the exchange anisotropy constants.

Influence of magnetic anisotropy on hysteresis behavior in the two-spin model of a ferro/antiferromagnet bilayer with exchange bias

“…Magnetization curves if Fig. 2 demonstrate experimentally observed [4,5] features, such as inclined segments and horizontal plateaus.…”

“…At the same time, coercivity is increased greatly. In recent experiments [4,5] asymmetric hysteresis loops, inclined segments of the ( ) = M M H curves, and the horizontal plateaus (steps) in the M(H) curves were observed. This complicated behavior is not caused by the kinetics of the magnetization reversal (by the finite rate of the field change in the experiment) and it is apparently caused by certain nonuniform and noncolinear (canted) states of the magnetic layers.…”

Properties of ferromagnetic film hysteresis, on the surface of a hard-magnetic antiferromagnet, with a domain structure

“…2,[4][5][6][7][8] However, the EB is observed even in the case of a compensated boundary, and can be explained by non-ideality (roughness) of the interface. The latest experiments have shown [9][10][11] that aside from EB, the field dependence of magnetization can have additional, and fairly complex properties: the appearance of a "horizontal plateau" with constant magnetization in a range of fields, the differing of the slope of the M ¼ M(H) dependence, in accordance to different field values, and the hysteresis loop itself "splitting" into two symmetrical or asymmetrical loops.…”

Field dependences of the magnetization and exchange bias in ferro/antiferromagnetic systems. II. Continuum model of a ferromagnetic layer

“…Recently, new features of the EB phenomenon have been found experimentally: the shifted hysteresis loop becomes asymmetric ͑i.e. M͑2H bias − H͒ −M͑H͒͒ and steps appear on it, [11][12][13][14][15] and the slope of the magnetization curve is different on different sections. The presence of "small shelves" and sections of the function M͑H͒ which are separated by field intervals indicates the possible existence of stationary states which are different from completely magnetically reversed states.…”