Magnetic coupling and low-energy excitations in NdGa2 studied by ESR

Magnetic coupling and low-energy excitations of NdGa2 were studied by elect ron-spin resonance (ESR) and magnetic-susceptibility measurements between r oom temperature and 4 K. Only the conduction-electron ESR resonance was det ected, whereas the f-electron resonances, due to the effects of the crystal line electric held and the sf indirect exchange interactions, are shifted o utside the range of the X-band ESR experiment. In the high-temperature regi me between 300 and 100 K the ESR susceptibility appears as Pauli-like where as below 100 K it shows an enhancement due to the sf exchange and follows t he temperature dependence of the Curie-Weiss-type f-electron magnetic susce ptibility. The f-electron magnetism is observed indirectly via the enhancem ent effect on the conduction electrons, demonstrating the importance of the exchange interactions in NdGa2. Magnetization measurements with a supercon ducting quantum interference device magnetometer have demonstrated that the nature of the reported ferromagnetic component below 5 K is not. that of a true ferromagnet. Rather, the magnetization is field induced and decays to zero after switching off the external magnetic field. A nonresonant microw ave absorption, reported previously for canted antiferromagnets, was observ ed in the antiferromagnetic phase. [S0163-1829(99)15033-1].