Determination of the magnetization distribution in Cr₂O₃using spherical neutron polarimetry

Abstract

The magnetization distribution due to the Cr3+ ion in Cr2O3 has been determined using spherical neutron polarimetry. The magnetic structure factors of h 0 l reflections have been measured out to sin θ/λ = 0.75 Å-1. The results show that the Cr3+ magnetic moment is reduced by the zero-point spin deviation and by covalent mixing to 2.48 µB. They are consistent with the Cr d electrons being in the trigonally symmetric a1 and e orbitals derived from the cubic orbitals with t2g symmetry. There is a small but significant magnetization which is not accounted for by these orbitals, which is attributed to covalent overlap. Its symmetry is consistent with the magneto-electric susceptibility.

Ferromagnetic superexchange in insulatingCr2MoO6by controlling orbital hybridization

“…GGA+U indeed opens up a band gap and increases the Cr 3+ magnetic moment from ~2.5 µ B for GGA to ~2.9 µ B for GGA+U. Reduction from 3.0 µ B to 2.9 µ B is due to the covalency and comparison with the experimental value, 2.47 µ B , suggests that effect of quantum spin fluctuation is important in this system [16,17,18]. Note that in our electronic structure calculations, the principle axis is along the tetragonal axes which are not aligned with the cubic axis of the local crystal field of the CrO 6 system, which gives rise to the mixture of both t 2g and e g states in the former coordinate system for Cr 3d orbitals.…”

“…The magnetic signal disappears at the antiferromagnetic transition temperature T N ~ 93 K, consistent with the specific heat measurement. Note that the magnitude of the static magnetic moment (≈ 2.47 μ B /Cr) extracted from NPD measurement is smaller than the theoretical value of 3.0 μ B /Cr, which is attributed to quantum spin fluctuation (at low T) as well as due to the covalence [16,17,18].…”

Magnetoelectric properties of 500-nmCr2O3films

“…[3] after a purely magnetic FC in a positive H fc = 5 kOe. Analysis of the spin structures in Cr 2 O 3 using spherical neutron polarimetry [27][28][29] demonstrated that ME cooling in antiparallel E fc and H fc yields the AF domain type with the positive top magnetization, as shown in Fig. 7.…”

Superexchange theory of electronic polarization driven by relativistic spin-orbit interaction at half filling

“…, which crystallizes in the corundum structure (the space group is R3c) [28]. The formal configuration of the Cr-ions in Cr 2 O 3 is 3d 3 .…”