Abstract
GdN and SmN are two of the lanthanide nitrides, most of which are intrinsic ferromagnetic semiconductors. Superlattices comprising the pair offer a unique opportunity to investigate heterojunctions that feature simultaneous conductivity and magnetic interface influences. Here we report an investigation of these influences, using magnetisation and X-ray magnetic circular dichroism for magnetic effects, and magnetoresistance and Hall effect studies of their electrical conductance. Magnetic data show clear signatures of a conflicting Zeeman vs. interfacial exchange and the magnetic disruption that results, while resistivity and Hall measurements show conduction in both GdN and SmN.
Highlights
Semiconductor heterojunctions have become some of the most important structures within electronics technology, opening the door to confined electron gases, tunneling structures, high electron-mobility transistors, quantum well lasers and much more.[1,2,3,4] Ferromagnetic hetero-interfaces have likewise driven technological advances: giant magnetoresistance and tunneling magnetoresistance random access memory (MRAM) to mention just two.[5]
The implication is that a 1.5 nm SmN layer does not fully block GdN/GdN exchange; the exchange spring in SmN does not impact on the alignment at the two interfaces
Exchange blocking is accomplished by 5 nm of SmN, and thereafter the magnetic response changes little with increasing SmN thickness, supporting the loss of interfaceexchange spin alignment across a few nm of SmN
Summary
Semiconductor heterojunctions have become some of the most important structures within electronics technology, opening the door to confined electron gases, tunneling structures, high electron-mobility transistors, quantum well lasers and much more.[1,2,3,4] Ferromagnetic hetero-interfaces have likewise driven technological advances: giant magnetoresistance and tunneling magnetoresistance random access memory (MRAM) to mention just two.[5]. The strong spin–orbit interaction and weak crystal-field influence on the 4 f shell ensures that the magnetisation of ferromagnetic SmN is vanishingly small, corresponding to ∼ 0.035 μB per Sm3+ ion.[9,18] X-ray magnetic circular dichroism (XMCD) and anomalous Hall effect measurements identify that it is the orbital component that dominates the net magnetic moment, so that the 4 f spin magnetic moment in SmN is antialigned to an applied field.[10,19] Its magnetocrystalline anisotropy, though somewhat larger than that of GdN, is small. The present paper reports magnetisation, XMCD and anomalous Hall effect studies of the conflict’s influence on the magnetic alignment in GdN/SmN superlattices
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