Giant anomalous Hall effect in epitaxial Mn3.2Ge 3.2 Ge films with a cubic kagome structure

We report on the first example of epitaxial Mn3+delta Ge 3 +delta Ge thin films with a cubic L 1 2 structure. The films are found to exhibit frustrated ferromagnetism with an average magnetization corresponding to 0.98 . 98 +/- 0.06 . 06 mu B/Mn, B / Mn, far larger than the parasitic ferromagnetism in hexagonal Mn3Ge 3 Ge and the partially compensated ferrimagnetism in tetragonal Mn3Ge. 3 Ge. The Hall conductivity is the largest reported for the kagome magnets with a low-temperature value of Q xy = 1587 S/cm. / cm. Density functional calculations predict that a chiral antiferromagnetic structure is lower in energy than a ferromagnetic configuration in an ordered stoichiometric crystal. However, chemical disorder driven by the excess Mn in our films explains why a frustrated 120 degrees degrees spin structure is not observed. Comparisons between the magnetization and the Hall resistivity indicate that a noncoplanar spin structure contributes the Hall signal. Anisotropic magnetoresistance and planar Hall effect with hysteresis up to 14 T provides further insights into this material.