Magnetism at spinel thin film interfaces probed through soft X-ray spectroscopy techniques

Abstract

Magnetic order and coupling at the interfaces of highly spin polarized Fe3O4 heterostructures have been determined by surface sensitive and element specific soft x-ray spectroscopy and spectromicroscopy techniques. At ambient temperature, the interface between paramagnetic CoCr2O4 or MnCr2O4 and ferrimagnetic Fe3O4 isostructural bilayers exhibits long range magnetic order of Co, Mn and Cr cations which cannot be explained in terms of the formation of interfacial MnFe2O4 or CoFe2O4. Instead, the ferrimagnetism is induced by the adjacent Fe3O4 layer and is the result of the stabilization of a spinel phase not achievable in bulk form. Magnetism at the interface region is observable up to 500 K, far beyond the chromite bulk Curie temperature of 50-95 K.

Unconventional switching behavior in La0.7Sr0.3MnO3/La0.7Sr0.3CoO3 exchange-spring bilayers

“…31 The Co difference curve shows more multiplet structures on the L 3 edge, and the overall line profile matches well with that of Co 2þ in a similar octahedral bonding environment (e.g., as in CoFe 2 O 4 ). 32 These results indicate an increase in Mn 4þ concentration and the presence of Co 2þ in the bilayer. We 37 could exist as well.…”

Tuning interfacial exchange interactions via electronic reconstruction in transition-metal oxide heterostructures

“…3(a)) and a CoFe 2 O 4 thin film (50 nm thickness) in which the Co 2þ ions predominantly occupy octahedral sites in the spinel structure. 24 For both detection modes, a clear dependence of the Co multiplet structure at the L 3 edge on the LSCO layer thickness was observed. The Co-XA spectrum for sample CM2 strongly resembles that of CoFe 2 O 4 showing an unexpected Co 2þ valence state (features A, B, and C).…”

Geometrical lattice engineering of complex oxide heterostructures: a designer approach to emergent quantum states

“…Another important issue is related to cation disorder or a mixture of various cation valences that can occur during the growth of spinel films [41][42][43][44][45][46] and if present it may potentially destroy the expected normal spinel stacking patterns. Thus, it fine multiplet features) almost identical to those of the CCO bulk samples implying the absence of any detectable cation distribution disorder or mixture of chemical valences.…”