Magnetic order by C-ion implantation into Mn5Si3 and Mn5Ge3 and its lateral modification

Abstract

Ferromagnetic Mn5Si3C0.8 and Mn5Ge3C0.8 films with Curie temperatures TC well above room temperature are obtained by C+12-ion implantation in antiferromagnetic Mn5Si3 or ferromagnetic Mn5Ge3. Patterning of the films with a gold mesh serving as a stencil mask during implantation allows a lateral modification of magnetic order creating ferromagnetic regions of Mn5Si3C0.8 which are embedded in antiferromagnetic Mn5Si3. This provides a procedure for the fabrication of magnetoelectronic hybrid devices comprised of different magnetic phases.

Large topological Hall effect in the non-collinear phase of an antiferromagnet

“…The temperature-independent Hall coefficients R 0 and S H and the linear r xx (T) behaviour support the classification of Mn 5 Si 3 C 0.8 as a metallic ferromagnet. This is in line with previous investigations 31, 49 and presumably originates from superexchange between Mn 2 moments via carbon as reported for Mn 5 Ge 3 C x (ref. 29).…”

Simulation of the enhanced Curie temperature in Mn5Ge3Cx compounds

“…This conclusion follows from our electronic structure calculations for the relaxed Mn 5 Ge 3 C system with the empty spheres at carbon positions ͑further referred to as Mn 5 Ge 3 V C ͒. The calculated magnetic moments on Mn agree well with the average saturated moment of 2.2 B / Mn, observed for the C-implanted Mn 5 Ge 3 C 0.8 films, 4 but deviate from those obtained for the sputtered samples, where the largest moment of 1.1 B / Mn was observed for Mn 5 Ge 3 C 0.75 . 3 This discrepancy could be ascribed to disorder effects and defects formation, which may differ in sputtered and implanted samples.…”

“…The carbon implanted Mn 5 Ge 3 C 0.8 films were found to exhibit magnetic properties very similar to their sputtered counterparts. 4 The average saturated moment of 2.2 B / Mn was observed for C-implanted Mn 5 Ge 3 C 0.8 films ͑1.1 B / Mn in the sputtered samples͒ and turned to be somewhat smaller than 2.6 B / Mn of Mn 5 Ge 3 polycrystals. 4 At the same time, the isostructural antiferromagnetic ͑AFM͒ Mn 5 Si 3 with T N = 98 K was reported to exhibit ferromagnetism when doped with carbon, with the transition temperature reaching 350 K in Mn 5 Si 3 C 0.8 .…”

“…4 The average saturated moment of 2.2 B / Mn was observed for C-implanted Mn 5 Ge 3 C 0.8 films ͑1.1 B / Mn in the sputtered samples͒ and turned to be somewhat smaller than 2.6 B / Mn of Mn 5 Ge 3 polycrystals. 4 At the same time, the isostructural antiferromagnetic ͑AFM͒ Mn 5 Si 3 with T N = 98 K was reported to exhibit ferromagnetism when doped with carbon, with the transition temperature reaching 350 K in Mn 5 Si 3 C 0.8 . 5 While in Mn 5 Si 3 C x films the interstitial carbon leads to a lattice expansion, the increase of T C upon doping in Mn 5 Ge 3 C x is accompanied by a lattice compression.…”

Hanle-effect measurements of spin injection from Mn5Ge3C0.8/Al2O3-contacts into degenerately doped Ge channels on Si

“…Spin injection was demonstrated in Ge by using tunnel contacts [14][15][16] and Schottky contacts. 17 Mn 5 Ge 3 is a ferromagnet (FM) with a Curie temperature T C  300 K 18,22 that can be enhanced by C-doping up to T C = 450 K. [19][20][21] Cdoped Mn 5 Ge 3 C x has a negligible conductivity mismatch with highly doped Ge 22 , which makes it particularly interesting as a contact material for spin injection into Ge. Furthermore, Mn 5 Ge 3 C x can be grown epitaxially on Ge (111) 21 , which could help to avoid the formation of interface defects and hence improve the spin injection/detection efficiency.…”