Browsing by Author "Kriegner, Dominik"

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Large anomalous Nernst effect in thin films of the Weyl semimetal Co2MnGa
(2018-11-19)
Reichlova, Helena
;
Schlitz, Richard
;
Beckert, Sebastian
;
Swekis, Peter
;
Markou, Anastasios
The magneto-thermoelectric properties of Heusler compound thin films are very diverse. Here, we discuss the anomalous Nernst response of Co2MnGa thin films. We systematically study the anomalous Nernst coefficient as a function of temperature, and we show that unlike the anomalous Hall effect, the anomalous Nernst effect in Co2MnGa strongly varies with temperature. We exploit the on-chip thermometry technique to quantify the thermal gradient, which enables us to directly evaluate the anomalous Nernst coefficient. We compare these results to a reference CoFeB thin film. We show that the 50-nm-thick Co2MnGa films exhibit a large anomalous Nernst effect of -2 mu V/K at 300 K, whereas the 10-nm-thick Co2MnGa film exhibits a significantly smaller anomalous Nernst coefficient despite having similar volume magnetizations. These findings suggest that the microscopic origin of the anomalous Nernst effect in Co2MnGa is complex and may contain contributions from skew-scattering, side-jump, or intrinsic Berry phase. In any case, the observed anomalous Nernst coefficient of -2 mu V/K at 300 K is large compared to the values measured in other thin films and makes this material system a very promising candidate for efficient spin-caloritronic devices. Published by AIP Publishing.
Thickness dependence of the anomalous Hall effect in thin films of the topological semimetal Co2MnGa
(2019-08-19)
Markou, Anastasios
;
Kriegner, Dominik
;
Gayles, Jacob
;
Zhang, Liguo
;
Chen, Yi-Cheng
Topological magnetic semimetals promise large Berry curvature through the distribution of the topological Weyl nodes or nodal lines and further novel physics with exotic transport phenomena. We present a systematic study of the structural and magnetotransport properties of Co2MnGa films from thin (20 nm) to bulklike behavior (80 nm) in order to understand the underlying mechanisms and the role of topology. The magnetron sputtered Co2MnGa films are L2(1)-ordered showing very good heteroepitaxy and a strain-induced tetragonal distortion. The anomalous Hall conductivity was found to be maximum at a value of 1138 S/cm, with a corresponding anomalous Hall angle of 13%, which is comparatively larger than topologically trivial metals. There is good agreement between the theoretical calculations and the Hall conductivity observed for the 80 nm film, which suggests that the effect is intrinsic. Thus, the Co2MnGa compound manifests as a promising material for topologically driven spintronic applications.