Nuclear Magnetic Resonance Study of the Easy Axis of Magnetization in Manganese Bismuthide

Abstract

The zero-field NMR of Mn 55 in ferromagnetic MnBi has been observed in the temperature range 4.2°K to 500°K. Resonance signals from nuclei in the domain and domain wall are separately observed at 225.01 MHz, and 206 MHz, respectively, at 294°K. As the temperature is decreased, the quadrupole splitting and the frequency of the central line for the domain signal decrease gradually below 142°K and a temperature somewhat lower than 142°K, respectively, and change abruptly at 90°K. These results show that below 142°K the magnetic moment deviates gradually from the c -axis and flops into the c -plane at 90°K. The temperature dependence of the NMR intensity has also been observed, from which a qualitative temperature variation of the anisotropy constant K 1 has been obtained. The hyperfine field and e 2 q Q / h extrapolated to 0°K are -224.5 kOe and 14.0 MHz, respectively.