We report a study of enhancing the magnetic ordering in a model magnetically doped topological insulator (TI), Bi(2-x)Cr(x)Se(3), via the proximity effect using a high-TC ferrimagnetic insulator Y(3)Fe(5)O(12). The FMI provides the TI with a source of exchange interaction yet without removing the nontrivial surface state. By performing the elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally observed an enhanced TC of 50 K in this magnetically doped TI/FMI heterostructure. We have also found a larger (6.6 nm at 30 K) but faster decreasing (by 80% from 30 to 50 K) penetration depth compared to that of diluted ferromagnetic semiconductors (DMSs), which could indicate a novel mechanism for the interaction between FMIs and the nontrivial TIs surface.

Nanoscale Fe 3 O 4 epitaxial thin film has been synthesized on MgO/GaAs(100) spintronic heterostructure, and studied with X-ray magnetic circular dichroism (XMCD). We have observed a total magnetic moment (m l+s ) of (3.32±0.1)µ B /f.u., retaining 83% of the bulk value. Unquenched orbital moment (m l ) of (0.47µ B ±0.05)µ B /f.u. has been confirmed by carefully applying the sum rule. The results offer direct experimental evidence of the bulk-like total magnetic moment and a large orbital moment in the nanoscale fully epitaxial Fe 3 O 4 /MgO/GaAs(100) heterostructure, which is significant for spintronics applications. Liu et al. CITATION:

Abstract:The spin and orbital magnetic moments of the Fe 3 O 4 epitaxial ultrathin film synthesized by plasma assisted simultaneous oxidization on MgO(100) have been studied with X-ray magnetic circular dichroism (XMCD). The ultrathin film retains a rather large total magnetic moment, i.e. (2.73±0.15)μ B /f.u., which is ~ 70% of that for the bulk-like Fe 3 O 4 . A significant unquenched orbital moment up to (0.54±0.05) μ B /f.u. was observed, which could come from the symmetry breaking at the Fe 3 O 4 /MgO interface. Such sizable orbital moment will add capacities to the Fe 3 O 4 -based spintronics devices in the magnetization reversal by the electric field.

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