Magnetic proximity coupling to Cr-doped Sb2Te3 thin films

Abstract

Using soft x-ray absorption spectroscopy we determined the chemical and magnetic properties of the magnetic topological insulator (MTI) Cr:Sb 2 Te 3 . X-ray magnetic circular dichroism (XMCD) at the Cr L 2,3 , Te M 4,5 , and Sb M 4,5 edges shows that the Te 5p moment is aligned antiparallel to both the Cr 3d and Sb 5p moments, which is characteristic for carrier-mediated ferromagnetic coupling. Comparison of the Cr L 2,3 spectra with multiplet calculations indicates a hybridized Cr state, consistent with the carrier-mediated coupling scenario. We studied the enhancement of the Curie temperature, T C , of the MTI thin film through the magnetic proximity effect. Arrott plots, measured using the Cr L 3 XMCD, show a T C ≈ 87 K for the as-cleaved film. After deposition of a thin layer of ferromagnetic Co onto the surface, the T C increases to ∼93 K, while the Co and Cr moments are parallel. This increase in T C is unexpectedly small compared to similar systems reported earlier. The XMCD spectra demonstrate that the Co/MTI interface remains intact, i.e., no reaction between Co and the MTI takes place. Our results are a useful starting point for refining the physical models of Cr-doped Sb 2 Te 3 , which is required for making use of them in device applications.

Magnetic-impurity-induced modifications to ultrafast carrier dynamics in the ferromagnetic topological insulators Sb2−xVxTe3

“…The observed Sb 5p magnetic moment at the non-magnetic element is most likely induced by the V magnetic dopant. This result is in good agreement with the previous XMCD studies for Cr-or V-doped compounds [29,33,35,36,38]. More importantly, very small but clear XMCD signals are observed at the Te M 4,5 absorption edges.…”

“…The microscopic origin of the ferromagnetism and the QAH state has been extensively investigated by theoretical and experimental approaches [26][27][28][29][30][31][32][33][34][35][36][37][38]. Element-specific x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) experiments revealed that the long-range ferromagnetic order in the magnetic TIs is caused by a magnetic coupling between p-d electrons of the host and magnetic dopants because the clear XMCD signals were observed not only at V (Cr) sites but also at Sb sites [29,33,35,36,38]. In addition, first principles calculations, scanning tunneling microscopy/spectroscopy (STM/STS) and resonant photoemission spectroscopy identified the impurity states of vanadium dopants at or near the Dirac node [26,30,32,36].…”

Direct observation of proximity-induced magnetism and spin reorientation in topological insulator on a ferrimagnetic oxide

“…The XMCD at Fe L 3 and Te M 5 edges features opposite signs, pointing down for Fe L 3 and pointing up for Te M 5 . This reveals the FM coupled nature between these two elements defined by the inverse electronic transition symmetry, [14][15][16] which is discussed in the following paragraph. Figure 2(d) presents the full range XMCD survey across the Te M 4 and M 5 edges using r(þ) along with the result by r(À).…”

“…2(c XMCD at the Te M 5 edge represents a magnetic moment on the Te's valence orbit 14,15 resulting from the interfacial orbital hybridization with Fe 3d or Tm 4f after introducing an adjacent TIG. Consequently, the opposite sign of XMCD at the Fe L 3 and Te M 5 edges at 20 K reveals that the magnetic moment on the Te 5p-orbit is FM coupled with Fe 3d 14,15 referring to their inverse electronic transition symmetry, 2p!3d for Fe L 3 and 3d!5p for Te M 5 . 14,15 Hence, Tm 4f and Te 5p are AFM coupled.…”

Topological quantum weak antilocalization limit and anomalous Hall effect in semimagnetic Bi2−xCrxSe3/Bi2Se3−yTey heterostructure

“…This is comparatively two orders higher than bulk and epitaxial films of Bi 2 Se 3 and Bi 2 Te 3 [36]. Furthermore, higher concentration of Cr (x>0.20) supplies more free charge carriers in the form of holes in Bi 2 Te 3, Sb 2 Te 3 and electrons in Bi 2 Se 3 as a result of impregnable chemical potential disorder around the Dirac point [36,38]. We conclude that this scenario would be a descriptive of non-localized bulk carrier scattering rather than localized Dirac surface electrons in the vicinity of T c for this heterostructure.…”