Chemically induced magnetism and magnetoresistance in La0.8Sr1.2Mn0.6Rh0.4O4

It is shown by magnetometry and mu SR spectroscopy that short-range magneti c interactions between the Mn cations in the nonmetallic K2NiF4-like phase La0.8Sr1.2Mn0.6Rh0.4O4 become significant below similar to 200 K. Negative magnetoresistance (rho/rho (0) similar to 0.5 in 14 T at 108 K) is apparent below this temperature. Neutron diffraction has shown that an applied magn etic field of 5 T is sufficient to induce saturated (3.38(7)mu (B) per Mn) long-range ferromagnetic ordering of the atomic moments at 2 K, and that th e induced ordering persists up to a temperature of 50 K in 5 T. Spin glass behavior is observed below 20 K in the absence of an applied field. The ind uced magnetic ordering is attributed to the subtle changes in band structur e brought about by the external field, and to the controlling influence of Rh3+ over the relative strength of competing magnetic exchange interactions .