Field induced metamagnetic transition of ErCo3 studied by NMR

Abstract Magnetic field dependence of Co 59 NMR resonance frequencies in ferrimagnetic ErCo 3 was measured in fields parallel and perpendicular to the c -axis of the crystal up to 8 T at 4.2 K. The zero field powder spectrum at 4.2 K shows three resolved lines at 23, 65, and 96 MHz, which correspond to 3b, 6c, 18h sites of Co, respectively. When field is applied along the c -axis, the resonance frequencies of 96 MHz line increase at about 10.01 MHz/T with increasing field, while those of 23 and 75 MHz lines decrease at the same rate. This means that the hyperfine field H hf is negative only for the Co 18h site, whereas at 3b- and 6c-Co it is positive. The positive H hf is resulted from a large contribution of unquenched 3d orbital moments. When field is applied perpendicular to the c -axis, the frequencies of all three resonance lines increase with increasing field, which means that H hf is negative at all the three Co sites. The resonance frequencies abruptly change around the field between 2 and 3 T due to the field induced metamagnetic transitions caused by the rotations of Er and Co magnetic moments towards the direction of the applied field from the c -axis.