Magneto-optics observation of spontaneous domain structure in ferromagnetic La_0.78Ca_0.22MnO₃single crystal

Abstract

Spontaneous ferromagnetic domains in lightly Ca-doped La1−xCaxMnO3 single crystals have been visualized and investigated by means of the magneto-optical technique. In marked difference to the magnetic contrast structures associated with magneto-crystalline anisotropy, which appear only in applied magnetic field, spontaneous ferromagnetic domains show up at low temperatures below the Curie temperature in zero applied field and are characterized by oppositely oriented spontaneous magnetization in adjacent domains. Ferromagnetic domains seen in zero field cooled samples take the form of almost periodic, corrugated stripe-like structures. Application of even a very weak magnetic field during cooling through the magnetic ordering transition changes the stripe domain structures into a bubble domain system.

Study of the micromagnetic structure of a La0.7Sr0.3MnO3film

“…These comprise magneto-optical techniques [3][4][5][6][7], magnetic force microscopy (MFM) [8][9][10][11][12][13][14][15][16][17][18], scanning SQUID and scanning Hall probe microscopy [19,20], spin-polarized scanning tunnelling microscopy [21], Bitter decoration [22] and Lorentz electron microscopy [23]. Most of the studies are focused on the interplay between structural and magnetic domains [5,7] as well as electronic phase separation [19,22] in case of single crystals and on strain effects in case of thin films [9, 13-15, 17, 24]. It has been well established that compressive strain leads to an uniaxial anisotropy with the substrate normal as easy axis and a clear maze-or stripe-like perpendicular magnetic domain pattern.…”

Ferromagnetic domain structure ofLa0.78Ca0.22MnO3single crystals

“…The applied magnetic field, up 500 Gauss, the maximum field available in our MO setup, does not change the domains orientation and neither modifies significantly their width. 8 On the basis of the MO investigations we conclude that magnetic domain walls are pinned to the structural twin domain boundaries.…”

“…As we have pointed out in our earlier paper, these are the conditions under which unambiguous MO image of the Weiss domains can be obtained. 8 The magnetic contrast associated with ferromagnetic domains appears immediately below T C . The Weiss domains are revealed as zigzagging series of dark and bright stripes.…”

“…The bright and dark regions in the MO image correspond to areas with opposite perpendicular component of the stray field, caused by opposite directions of the spontaneous magnetization in adjacent domains. 8 The domains boundaries follow the intersections of (011) and (011) cubic orientation. The applied magnetic field, up 500 Gauss, the maximum field available in our MO setup, does not change the domains orientation and neither modifies significantly their width.…”

Temperature Dependence of Magnetization Reversal of Thin Manganite Film

“…The domain structure is very sensitive to all mentioned above defects and could highlight not only the scale of magnetic ordering, but the defect distribution, too [8,9]. However, despite a long study of manganites [10,11], little is known about the magnetic domain structure of bulk and especially thin film manganites [12]. According to a few available publications concerning direct visualization of magnetic domains in films, domains with perpendicular spontaneous magnetization are observed in the films with thickness below 100 nm [13][14][15].…”