Magnetization reversal in epitaxial MnAs thin films

Abstract

The magnetization reversal process of MnAs epitaxial films grown on semiconductor substrates was investigated by magneto-optical Kerr effect (MOKE) microscopy, magnetic hysteresis, and magnetoresistance measurements. While the stripe patterns with opposite magnetization in the α-phase of MnAs have been observed previously, we have observed domain dynamics on a vastly different length scale. MOKE images revealed domain nucleation and avalanche domain reversal, which are a collective behavior resulting from interactions among a large number of α-phase regions. The observed reversal processes are reflected in the magnetic hysteresis and magnetotransport measurements. These effects are strongly film thickness dependent.

Threshold MnAs thickness for the formation of ordered α/β stripes in MnAs/GaAs(001)

“…A much lower value may be inferred from the MFM work of Fraser et al [26], which mentions the presence of α/β stripes with a period of 230 nm in a 10 nm thick sample. Unfortunately, no image is provided in the article to support this statement.…”

“…Experimental studies exist on thin MnAs layers on GaAs(001), demonstrating that the crystal structure is well defined and relaxed for films a few nm thick [21] and that the α/β phase coexistence as a function of temperature is observed already for very thin films [22]. Other studies [23][24][25][26][27] report, albeit with some contradictory results, images of the local magnetic order in thin (<50 nm) MnAs layers. Finally, the role of the layer thickness has been evoked also in connection with the electronic and magnetic properties of ~µm-sized laterally confined MnAs ribbons [27,28].…”