Spin polarization asymmetry at the surface of chromia

Boundary magnetization properties of epitaxialCr2−xAlxO3thin fi

“…On the other hand, the average value = 0.73 ± 0.07 that we have determined from our experiments is consistent within the statistically estimated error with the critical exponent value = 0.78 ± 0.02 that was predicted by Binder for the surface magnetization of a 3D Ising model. Thus, the critical behavior we observe in our samples here can also be considered as corroborating the large body of experimental evidence that identifies the remnant ferromagnetic signal observed in epitaxial Cr 2 O 3 and Cr (2-x) Al (x) O 3 films as boundary magnetization [10,11,12,13]. The estimated error that we assigned to the average critical exponent above is the standard deviation of the mean.…”

“…Correspondingly, the XRD peak positions in our samples shift from diffraction angles of 39.75° (0006) and 33.6° (10)(11)(12)(13)(14) for the pure Cr 2 O 3, towards the Al 2 O 3 (0006) and (10-14) diffraction peaks upon increasing x. This x-dependent peak shift in the absence of significant broadening verifies the simple Cr 3+ substitution by Al 3+ and the corresponding formation of isovalent solid solutions type samples in the entire range between x = 0 and x = 0.6.…”

“…This is the case in a single crystalline magnetoelectric antiferromagnet, which therefore can exhibit an equilibrium net magnetization at the boundary. In Chromia, this boundary magnetization (BM) exists at the (0001) surface [9,10,11]. The BM is fully coupled to the bulk antiferromagnetic (AF) order parameter and can be reversed together with it by a combination of E and H fields in bulk materials [8].…”

Moving towards the magnetoelectric graphene transistor

“…[1][2][3][4] While effective spin polarized carrier injection into graphene is a challenging problem, 5 an alternative is to exploit a magnetic insulator substrate or overlayer that can induce spin polarization in the graphene by interfacial spin interactions. 1,6-10 Cr 2 O 3 (0001) is a magnetoelectric, antiferromagnetic insulator with voltage switchable boundary magnetization; [11][12][13][14] while the bulk of the material exhibits no net magnetization, the 0001 surface possesses a well-defined moment whose direction may be reversed controllably by the application of an electric field. The presence of a significant net (nonzero) spin polarization at the Cr 2 O 3 (0001) interface is consistent with theoretical expectations 15 and has been demonstrated by spin polarized photoemission, 11 spin polarized inverse photoemission, 12,13 x-ray circular dichroism, 13 and spin polarized low energy electron microscopy.…”

“…The presence of a significant net (nonzero) spin polarization at the Cr 2 O 3 (0001) interface is consistent with theoretical expectations 15 and has been demonstrated by spin polarized photoemission, 11 spin polarized inverse photoemission, 12,13 x-ray circular dichroism, 13 and spin polarized low energy electron microscopy. 14 The huge surface spin polarization of chromia can be preserved at a buried interface, that is to say, the polarization may be retained even with an overlayer present. 14,16 Chromia is thus a promising magnetoelectric gate dielectric that has the potential to induce spin polarization in a graphene overlayer due to the proximity effect.…”