Positive linear magnetoresistance effect in disordered L21B-type Mn2CoAl epitaxial films

The inverse Heusler alloy Mn2CoAl is known as a spin gapless semiconductor (SGS). It is believed that the positive linear magnetoresistance (PLMR) effect observed at low temperatures indicates the quantum linear MR effect in the gapless electronic band structures near the Fermi level, i.e., evidence of the realization of a SGS [Ouardi et al., Phys. Rev. Lett. 110, 100401 (2013)]. For this reason, one presumes that the observation of the PLMR effect is indirect proof of the demonstration of XA-type Mn2CoAl consisting of the inverse Heusler structure. In this paper, we observe the PLMR effect at 10 K in homogeneous and single-phase Mn2CoAl epitaxial films grown by low-temperature molecular beam epitaxy at 100 degrees C. From anomalous x-ray diffraction measurements and analyses, we clarify that the 100 degrees C-grown Mn2CoAl epitaxial film is not composed of the XA-type structure but a disordered L2(1)B-type structure including some amount of Mn(A site) double left right arrow Co(C site) swapping and Mn(B site) double left right arrow Al(D site) swapping. On the basis of first-principles density-functional theory calculations, we discuss the correlation between the PLMR effect observed at 10 K and the possible electronic band structure in the disordered L2(1)B-type Mn2CoAl.

Automated summary

The study observed the positive linear magnetoresistance effect in Mn2CoAl alloy grown under certain conditions, and revealed its structure and electronic band characteristics through experiments and theoretical calculations.