Dominant carrier of pseudo-gap antiferromagnet Cr3Al thin film

Highlights: • Antiferromagnetic Cr3Al alloy film was a pseudo-gap semimetal. • Dominant carriers were evaluated by Hall and Seebeck effect measurements. • Dominant carrier of the film grown at 473 K was electron (hole) below (above) 285 K. • Change in the carrier would be relevant to the low effective mass of excited hole. Antiferromagnetic Cr_1-xAl_x with, x ~ 0.25, is a pseudo-gap semimetal. This study focuses the relationship between the pseudo-gap and the dominant carriers by comparing two films with the same composition but different chemical ordering. The film deposited at high temperatures with C11_b ordering exhibited a weak temperature dependence of resistivity and a positive Hall coefficient. In contrast, the film deposited at low temperature exhibited negative temperature dependence of resistivity and a change in the Hall coefficient from negative to positive with increasing temperature. The temperature derivative of the Seebeck coefficient, dα_s/dT, was positive for the C11_b ordered film, but reversed from negative to positive for the film without C11_b ordering. These results indicate that pseudo-gap formation is relevant to the change in the dominant carrier to electrons at low temperatures. Additionally, the change in the dominant carriers by temperature should be related to a low effective mass of holes.