communication of the ferromagnetic stratums of the obmenno-related systems by means of magnetostatic interaction

Thus, in the previous point the analysis of models with which help it is possible to feature magnetic properties of systems with exchange bias has been carried out, to predict quantity of effect and a coercive force.

These models, in particular, featured properties of double-layer structures. However in them interaction between two ferromagnetic stratums parted by an antiferromagnetic stratum is not considered.

In the given point such interaction is considered along with other mechanisms of interlaminar interaction between two ferromagnetic stratums, the parted intermediate stratum. The description of mechanisms of magnetic interlaminar interaction correlates also with the models of exchange bias featured in the previous point.

The magnetic structural systems containing an antiferromagnet as a layer, it is necessary to distinguish from other structures where as the intermediate stratum bottoms - or paramagnetic stratums act. Interlaminar communication of the first cannot be featured without a magnetic state of an antiferromagnetic stratum and proximity-effects on demarcations. In process of reduction of the size of system so-called źmagnetic poles╗, arising on surfaces of stratums, influence interactions in a stratum and between two ferromagnetic stratums. Such field dispersion quickly enough grows with reduction of a thickness of a dividing stratum.

If the intermediate stratum between two ferromagnetic is
Antiferromagnetic, such as, for example, Cr or Mp, he already cannot be considered as the "passive" medium transmitting an indirect exchange coupling, as in case of, for example, quantum hole where as a layer the diamagnet serves. In cases of an antiferromagnetic layer it is necessary to consider an exchange coupling of an antiferromagnet with a ferromagnetic on demarcations, and also an interior exchange coupling in an antiferromagnet. Solving distinction between an antiferromagnet and precious metal as the intermediate stratum consists that for an antiferromagnetic material each atom has a moment of magnet which is related to other atoms of an antiferromagnet, and, through the interface, with a ferromagnetic. Difficulty in understanding of properties of systems FM/AFM is caused by that the competition between an exchange interaction in a stratum and interphasic interaction FM/AFM can lead magnetic frustratsii when not all backs of the nearest neighbour can be in a local configuration of the underload energy.

The example such frustratsy is given in operation [63] where owing to unevennesses of interfaces arise frustratsii spins AFM, or FM, and there are domain walls, also, either in the AFM-LAYER, or in the Fm-layer. Occurrence of a domain wall in an antiferromagnet, parallel the interface, leads to reduction of an interphasic exchange interaction in system FM/AFM/FM. Interlaminar communication between two stratums FM through ideal intermediate stratum AFM (for lack of a roughness of interfaces) will tend or to parallel (ferromagnetic), or antiparallel (antiferromagnetic) communication. However, when on boundary there is a roughness, not all backs will be in their preferable state in an antiferromagnet, in a ferromagnetic, and also on the interface. Some steams of spins will bindingly be not in their underload energy configuration, i.e. The spin-spin coupling will be "frustrirovannoj" [64, 65].

In real intermediate stratums of fluctuation of a thickness will operate in the field spotted in length of the traversal response of a magnetic stratum, for averaging of contributions of communication from lateral fields of a different thickness. When an average
Bilinear interaction J1становится small enough as effect of fluctuation of a thickness of the intermediate stratum, the state with the least energy for structural system is found out when moments of magnet of magnetic stratums are perpendicular each other. It is a bottom of the model offered Slonchevsky [66], in which fluctuations ΔJ1 (n) in bilinear communication as communication J1 (n) changes a sign of one discrete stratum to the following are considered.

Other mechanism of interlaminar interaction of two Fm-layers is magnetostatic interaction. neel for the first time has studied the magnetostatic interaction arising between two magnetic stratums, with the magnetisations guided in planes of films, parted by an antimagnetic stratum [67]. This so-called “orange-peel” interaction is ferromagnetic when interfaces have the identical correlated sinuosity, and exponentially decreases with thickness of a dividing stratum.

It is often enough observed in magnetic structural systems and especially in spin gates [68]. Observation ostsillirujushchej interlaminar communication of type RKKI, related to oscillations in huge magnitosoprotivlenii in magnetic structural structures, has caused very major scientific interest. Such interaction also has been shown for systems FeCoV∕NiO∕FeCoV [69, 70].

The similar mechanism of magnetostatic interaction has been offered in operation Mauri [16] where it is supposed, that the roughness of stratums leads to formation of the compensated or not compensated fields on the interface owing to what on the interface fields are raised. Energy of magnetostatic interaction of this field, and also anisotropy of the AFM-LAYER can lead to formation of domains in an antiferromagnetic stratum. In turn the motion of these domain walls in the course of magnetisation reversal of the sample can reduce quantity of effect of exchange bias. Such model well works for a monocrystal antiferromagnet, and for
Polycrystalline AFM-LAYER the situation will develop more with difficulty, also depend and on crystalline structure of an antiferromagnet.

In case of magnetic films with terminating in the lateral sizes generation of "magnetic poles╗ near to the extremities leads to occurrence of the magnetic field termed as a degaussing field. Force of this field depends on geometry and magnetisation of the Fm-layer.

The elementary shape of magnetostatic interaction between two ferromagnetic films is an interaction by means of leakage fields. It arises that each ferromagnetic stratum is located in a magnetostatic field of dispersion of another. These two films will tend to orient the magnetisations antiparallelly to gain the closed magnetic flux. Effect of it is reduction of energy of Zeeman. Unlike the mediated interlaminar communication, magnetostatic communication is strongly nonuniform on the interface area. Though it is approximately uniform in the central field, but rashoditsja/deviates near to edges of the sample. For devices with the submicronic lateral sizes of a leakage field on edges can cause the considerable interaction [71].

Thus, in the available scientific literature ooze some mechanisms of interlaminar interaction between two ferromagnetic stratums, parted antiferromagnetic. Also presence of magnetostatic interaction in structures is scored. However it is necessary to score certain complexity of the description of the contribution of magnetostatic interaction in the full magnetic field energy of system owing to its impeded allocation among exchange interactions in thin-film structures C exchange bias.

One more method, allowing to show influence of magnetostatic interaction on the hysteresis curve shape it is featured in operation [72] and it is grounded on viewing of fields of interaction and allocation of fields of switching of the sample.


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A source: Gritsenko Christina Aleksandrovna. Features of processes of magnetisation reversal magnitostaticheski - and obmenno - the bound thin-film structures on the basis of permalloys. The dissertation on competition of a scientific degree of the candidate of physical and mathematical sciences. Kaliningrad - 2018. 2018

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