Observation of the magnetic structure in manganites by the high-resolution Bitter technique

Abstract

The magnetic structure of the doped perovskite manganites La0.7Sr0.3MnO3 and La0.8Ca0.2MnO3 at a temperature of 10 K has been investigated by using the decoration technique in a wide region of external magnetic fields (up to 1000 Oe). We observe the multidomain ferromagnetic state in La0.7Sr0.3MnO3 and the coexistence of the ferro-and nonmagnetic phases in La0.8Ca0.2MnO3. The dependence of the structure on an external magnetic field has been investigated in La0.8Ca0.2MnO3.

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 and twin domains in LCMO manganites

“…field images were featureless [2,12]. The correlations between magnetic and twin structures reported in Ref.…”

“…Surprisingly, little is known about domain structures in CMR manganite single crystals. Magnetic structures in manganites have been investigated using magneto-optical (MO) techniques [2][3][4][5][6], magnetic force microscopy [7][8][9], scanning SQUID and Hall probe microscopy [10,11], Bitter decoration [12], Lorentz electron microscopy [13,14], and neutron depolarization measurements [15]. Several papers present an evidence of magnetic structures below the Curie temperature, however, most of them appear only in applied magnetic field, contrary to what is expected for spontaneous ferromagnetic domains.…”

Magneto-optics observation of spontaneous domain structure in ferromagnetic La0.78Ca0.22MnO3single crystal

“…The image of the anisotropic field distribution on the surface of a ferromagnetic sample immersed in a uniform field can be easily confused with the expected image of spontaneous ferromagnetic domains. For example, in the reports on magneto-optical and high resolution Bitter investigations of La 0.7 Sr 0.3 MnO 3 and La 0.8 Ca 0.2 MnO 3 single crystals, the magnetic contrast has been seen only under applied field while the zero field images were featureless [6,23]. The correlations between magnetic and twin structures reported in [6] mean that the magnetic contrast observed in non-zero field has to be attributed to the magnetic crystalline anisotropy only, and not to the ferromagnetic domains.…”

“…Magnetic structures in manganites have been investigated experimentally by means of magneto-optical (MO) techniques [6][7][8][9][10][11][12][13], magnetic force microscopy (MFM) [14][15][16][17][18][19], scanning SQUID (SSM) and Hall probe microscopy (SHM) [20][21][22], Bitter decoration [23], Lorentz electron microscopy [24][25][26] and neutron depolarization measurements [27]. The last two techniques are clearly most suitable for resolving fine structures with domain sizes in the range of 10 µm and smaller.…”