Magnetic properties and anisotropic coercivity in nanogranular films of Co/Al₂O₃above the percolation limit

In-Plane Anisotropy Effect on Critical Transition Field in Nanogranular Films with Perpendicular Anisotropy

“…However, the magnetization reversal curves show that the film had attributes typical of a film with perpendicular anisotropy. This result was confirmed by the results of transmission electron microscopy obtained for the same film [21]. The peculiarities of the hysteresis sections in the M (H e ) curves for the film concerned allowed us to substantiate, in work [21], the statement that, in the magnetic aspect, the examined film is biphase; i.e.…”

“…As was mentioned above, we study an NG Co/Al 2 O n film with 74.4 at.% Co (f v ≈ 0.79), for which the percolation threshold is considerably exceeded. In the previous research [21], it was found that, in addition to the perpendicular magnetic anisotropy, this film also has in-plane anisotropy with the easy axis located in the film plane and oriented along the direction X. The electron microscopy research of the transverse cross-section of this film [21] showed that the specimen included both percolating clusters and non-percolating granules, and the relative fraction of the latter dominated.…”

“…4, b) axis of the in-plane anisotropy. Since, according to the estimations carried out in work [21], the contribution made by the percolating part of the film to its magnetization in the saturated state does not exceed 20%, the quantity θ m was calculated by equating derivatives (19) and (20) to zero and neglecting this contribution. In the inhomogeneous state, the moments of both subensembles deflect toward the equilibrium direction almost linearly, with a drastic ultimate transition into the homogeneous state; afterward, the direction of the magnetic moments in the single, united ensemble with ∆p = 1 asymptotically approaches the direction of H. The difference from the corresponding solutions obtained in work [10] mainly consists in the difference between the dependences θ 1 (H e ) and θ 2 (H e ) for various ϕ H .…”

“…At the magnetic reversal, they have to demonstrate features typical of films with perpendicular anisotropy. The researches of an NG film with bi-phase magnetic content corresponding to the presence of non-percolating granules and a percolation granular cluster in the film were carried out in work [21]. In this paper, the issues concerning the resolution of contributions from those two groups of granules to the magnetization reversal curves and the features in the angular dependence of the coercive field in such film were discussed.…”

“…We also considered the transition between the homogeneous and inhomogeneous magnetization states of such bi-phase film. Besides the perpendicular anisotropy, the granular part of this film has the in-plane one as well [21]. The conditions for the critical transition in the granular part of the film from the state with homogeneous orientation of magnetic moments to the inhomogeneous one and their dependence on the direction of a magnetizing field in the biaxially anisotropic film are analyzed.…”