Drastic changes of the domain size in an ultrathin magnetic film

Abstract

A general framework for the domain size in any ultrathin film with perpendicular magnetic anisotropy is here discussed. The domain structure is analyzed by using the classical theory taking into consideration the demagnetization field contribution to the domain wall energy. A sinusoidal model is considered to describe the domain structure while approaching, in two different cases, the monodomain state with in-plane magnetization. The first case is realized applying a large enough in-plane magnetic field. The second one is obtained by decreasing the perpendicular magnetic anisotropy, which is connected in many ultrathin systems with the increase of film thickness. A change in the domain size of several orders of magnitude is obtained while approaching the magnetization reorientation region. The minimal stripe domain period pϭ8ᐉ ex 2 /d is calculated from the sinusoidal model, where ᐉ ex is the exchange length and d is the thickness of the film. The range of possible domain size changes in ultrathin films is predicted. The domain size has been experimentally studied in a 1 nm Co film characterized by a square hysteresis loop. The investigations have been performed by polar Kerr based microscopy and magnetic force microscopy. The domain structure of two remnant states generated by applying an in-plane and a perpendicular magnetic field has been compared. Drastically, the smallest domain size has been observed for the former.

Spin excitation spectrum in a magnetic nanodot with continuous transitions between the vortex, Bloch-type skyrmion, and Néel-type skyrmion states

“…This change might be attributed to large size of the skyrmion and related edge effects or the large domain wall width related to the low value of Q factor. 34,35 Interestingly, the frequency of the breathing mode has a local minimum at every transformation of the magnetization configuration (between vortex and Bloch-like skyrmion, Bloch-like and Néel-like skyrmion, and Néel-like skyrmion and the vortex), while it is weakly dependent on the changes of Q for the Néel-like skyrmion. Fig.…”

New spin configurations in nano‐sized magnets near reorientation phase transition

“…During this evolution the domain size drastically changes, e.g. for cobalt films the domain period decreases in four -five orders of magnitude [5,8], see Figs. 5, 6.…”

“…The RPT could be also realized by applying in-plane magnetic field to a film with out-of-plane state. Domain size giant changes were observed approaching the RPT in infinite ultrathin films [5]. Domain-like magnetization distributions and their field-and/or thickness-driven evolutions were recently studied in such films experimentally, analytically, and by simulations [5][6][7][8].…”

Equilibrium and metastable nanoscale domains in ultrathin magnets

“…Other interesting examples of nonequilibrium systems are magnetic field-dependent biological processes in living cells [3]. In ultrathin films magnetic domains could be metatstable under influence of the coercivity, film morphology, domain nucleation barriers, and temperature changes [4][5][6]. For micrometers thick garnet films the thermal evolution of domain structures was described in [7].…”