Anomalous Hall effect in the half-metallic Heusler compound Co2TiX ( X=Si , Ge)

Abstract

Though Weyl fermions have recently been observed in several materials with broken inversion symmetry, there are very few examples of such systems with broken time reversal symmetry. Various Co2-based half-metallic ferromagnetic Heusler compounds are lately predicted to host Weyl type excitations in their band structure. These magnetic Heusler compounds with broken time reversal symmetry are expected to show a large momentum space Berry curvature, which introduces several exotic magneto-transport properties. In this report, we present systematic analysis of experimental results on anomalous Hall effect (AHE) in Co2TiX (X=Si and Ge). This study is an attempt to understand the role of Berry curvature on AHE in Co2TiX family of materials. The anomalous Hall resistivity is observed to scale quadratically with the longitudinal resistivity for both the compounds. The detailed analysis indicates that in anomalous Hall conductivity, the intrinsic Karplus-Luttinger Berry phase mechanism dominates over the extrinsic skew scattering and side-jump mechanism.

Atomic disorder and Berry phase driven anomalous Hall effect in Co2FeAl Heusler compound

“…3(a)) depicts that ρ xx increases with increasing temperature, indicating the metallic character of the compound. The residual resistance ratio (RRR = ρxx(300 K) ρxx(2 K) ) about 1.25 is similar to the reported value for other Co 2 -based Heusler compounds [25,51,52].…”

“…In order to elucidate the mechanism giving rise to AHE, we have plotted ρ AH versus ρ xx on a double logarithmic scale and fitting was employed to determine the exponent β using the relation ρ AH ∝ ρ xx β [25] as shown in FIG. 3(d).…”

“…Co 2 -based full Heusler compounds got enormous attention for their half-metallic behaviour, and 100% spinpolarization around Fermi level, which are the most prominent properties useful in spintronics devices and other memory-based applications [21][22][23][24]. Additionally, Co 2 -based Heusler compounds are of current interest, because of their large AHE due to the large Berry curvature linked with their band structure [17,[25][26][27][28]. Among Co 2based Heusler compounds, Co 2 FeAl is the most prominent candidate for the data processing and storage based applications due to its large Curie temperature(∼ 810 K to 900 K), high spin-polarization, low gilbert damping factor, and ultrafast magnetization dynamics [30][31][32][33].…”

Anomalous Hall effect from gapped nodal line in Co2FeGe Heusler compound

“…The residual resistance ratio (RRR= ρ xx (300K)/ρ xx (10K)) which quantifies the degree of disorder is 2.82. This value is larger than the most of Co 2based Heusler alloy [39,[59][60][61][62] signifies comparatively clean sample.…”

“…In order to investigate the origin of AHE, we analysed the ρ AH versus ρ xx on a double logarithmic scale. A linear fitting was employed to determine the exponent β according to the scaling relation ρ AH ∝ ρ xx β [62,64] shown in Fig. 3(d).…”