Magnetoresistance reversals and anomalous Hall effect in Mn3SnC and effects of carbon deficiency

The transport behavior of Mn₃SnC and Mn₃SnC_0.8compounds was investigated. Positive magnetoresistance (MR) and an anomalous Hall effect (AHE) are observed for each compound near respective Curie temperature,T_C. The positive MR is reversed during cooling fromT_Cbut is reentrant at low temperature. A 20% carbon deficiency of Mn₃SnC_0.8enlarges the positive MR atT_Cand shifts the temperatures for MR reversals. Ferromagnetic (FM) resonance measurements reveal that the MR reversals are related to the competition between FM and antiferromagnetic components of Mn atoms in each compound. A sign change of the Hall resistivity is observed during cooling of Mn₃SnC but not for Mn₃SnC_0.8. A scaling analysis suggests that the AHE in each compound is mostly due to an intrinsic contribution and that the intrinsic contribution is decreased by the carbon deficiency in Mn₃SnC_0.8.

High-Temperature Magnetism in Graphene Induced by Proximity to EuO

Addition of magnetism to spectacular properties of graphene may lead to novel topological states and design of spin logic devices enjoying low power consumption. A significant progress is made in defect-induced magnetism in graphene-selective elimination of p _z orbitals (by vacancies or adatoms) at triangular sublattices tailors graphene magnetism. Proximity to a magnetic insulator is a less invasive way, which is being actively explored now. Integration of graphene with the ferromagnetic semiconductor EuO has much to offer, especially in terms of proximity-induced spin-orbit interactions. Here, we synthesize films of EuO on graphene using reactive molecular beam epitaxy. Their quality is attested by electron and X-ray diffraction, cross-sectional electron microscopy, and Raman and magnetization measurements. Studies of electron transport reveal a magnetic transition at T_C^* ≈ 220 K, well above the Curie temperature 69 K of EuO. Up to T_C^*, the dependence R _xy( B) is strongly nonlinear, suggesting the presence of the anomalous Hall effect. The role of synthesis conditions is highlighted by studies of an overdoped structure. The results justify the use of the EuO/graphene system in spintronics.