Exchange bias

Interplay of chemical structure and magnetic order coupling at the interface between Cr2O3 and Fe3O4 in hybrid nanocomposites

“…The increase in coercivity and the small value of the exchange bias field H E associated with the EB effect indicate uniaxial and unidirectional exchange anisotropies due to the exchange interaction between the uncompensated surface spins of Cr 2 O 3 and Fe 3 O 4 in the nanocomposites. 31 The interfacial interaction between the magnetite and chromium oxide appears to be the main source of exchange bias, taking into account the exchange interaction that gives rise to magnetic order in the metal oxides. This interaction is often mediated through adjacent oxygen atoms and has a strong indirect exchange component that tends to favour an AFM alignment of the spins.…”

Perpendicular exchange bias in ferrimagnetic spin valves

“…Larger efforts were dedicated to the understanding of the FM/ AF EB systems with in-plane anisotropy of the ferromagnet 16 . Notably, Mangin and colleagues [17][18][19][20] have performed significant work on GdFe/TbFe ferrimagnetic soft/hard bilayers with in-plane anisotropy in which EB effects occur.…”

Probing Exchange Bias Effects in CoO/Co Bilayers with Pillar-Like CoO Structures

“…2,13) In fact, the magnitude of the coercivity enhancement and exchange bias in the disordered nanocomposite Co/CoO at 200 K appears to be higher than that reported for epitaxial thin films with similar blocking and measurement temperatures and nearly perfect interfaces. 14) This striking result suggests that pillar-like antiferromagnetic in-growths into the ferromagnet, along with an mixed array of disordered interfaces, can in-fact enhance the measured exchange bias effect, in qualitative agreement with the anomalously large natural exchange bias observed in Fe 2 O 3 /FeTiO 3 ores with a mixed microstructure.…”

“…The interfacial energy product E int for the mixed-interface film lies in the range 2.9-3.2 erg/cm 2 for all CoO thicknesses which is significantly higher compared with the interfacial energy for conventional Co/CoO bilayers that lie in the range (E int $ 0:1{0:8 erg/cm 2 ) for similar blocking temperatures. 13) …”

“…This result can be explained if the assumption is made that significant oxygen implantation into the Co only occurred during the growth of the first few monolayers of the CoO and stopped once the growing CoO exceeded a critical thickness, so that oxidization of the underlying cobalt layer was nearly equal in all cases, regardless of the final CoO thickness. The Néel temperature of CoO ($290 K in the bulk) 13) is below room temperature (298 K) and for this reason, no exchange bias is measured in the room temperature loops. Nonetheless it is possible that the coercivity enhancement observed at room temperature is the direct result of FM/AFM coupling, even though no exchange bias is observed, since this may be possible if the interfacial CoO moments have a locally enhanced T N as proposed for NiFe/ CoO 8) but are unstable against superparamagnetic activation.…”