Metamagnetism in Neptunium(V) Oxalate

摘要

Magnetic properties of neptunium(V) oxalate, (NpO2)2C2O4middot;4H2O, were studied from 2.4 to 37.5deg;K with magnetichyphen;susceptibility measurements using a vibratinghyphen;sample magnetometer at applied fields of 50ndash;10 000 Oe; Mouml;ssbauer spectra of the 59.54minus;keV ggr; ray in237Np were taken from 4.2 to 80deg;K. A metamagnetic transition was found at 11.6deg;K. Below 11.6deg;K the magnetization isotherms had the characteristic S shape of metamagnets. Below 8deg;K a pronounced hysteresis was observed as the field was reduced from saturation. At 3.15deg;K the remanent magnetization at 100 Oe was 96percnt; of the saturation magnetization at 10 000 Oe, and 125 times greater than the magnetization in the lowhyphen;moment state. The Mouml;ssbauer spectra exhibited magnetic hyperfine splitting which was independent of temperature, withg0mgr;nHeffequals; 10cmsol;sec;splitting above the transition temperature is attributed to a long paramagnetic relaxation time.