Boundary magnetization properties of epitaxial Cr2−xAlxO3 thin films

Authors

Lorenzo Fallarino, CIC nanoGUNE, San Sebastian, SpainFollow
Christian Binek, University of Nebraska-LincolnFollow
Andreas Berger, CIC nanoGUNE, San Sebastian, SpainFollow

Date of this Version

6-2-2015

Citation

PHYSICAL REVIEW B 91, 214403 (2015). DOI: 10.1103/PhysRevB.91.214403

Comments

Copyright (c) 2015 American Physical Society. Used by permission.

Abstract

The magnetoelectric antiferromagnet α-Cr₂O₃ (chromia) is known to possess a roughness insensitive net equilibrium magnetization at the (0001) surface, called boundary magnetization (BM), which is coupled to the bulk antiferromagnetic order parameter. In order to verify whether this symmetry sensitive BM persists in alloys, we investigate the impact of diamagnetic dilution on chromia thin films alloyed with the isostructural α-Al₂O₃ (alumina). Single-crystalline Cr_2−xAl_xO₃ thin films with (0001) surface orientation and varying stoichiometry have been grown by sputter codeposition in the concentration range between x = 0 and x = 0.6. For these samples, we find the corundum crystal structure, the antiferromagnetic ordering, and the boundary magnetization to be preserved. We also find that the critical temperature TN can be tuned by alloying with α-Al₂O₃, using the BM as a probe to study the magnetic phase transition. Furthermore, we were able to evaluate the critical exponent and the absolute BM values for different samples. Both properties corroborate that the observed magnetic signals originate from the BM rather than the bulk of the samples.