The Magnetic Susceptibility of Neptunium Oxide and Carbide between 4.2° and 350°K

Abstract

The magnetic susceptibilities of the dioxide and monocarbide of neptunium have been measured from 4.2 to 350°K. The inverse susceptibility of neptunium dioxide is linear in temperature above 60°K with an effective paramagnetic moment of 2.95 μ_B. A peak in the susceptibility‐vs‐temperature curve is observed at 25°K, in agreement with the maximum observed in the specific heat of NpO₂. The neptunium monocarbide becomes ferromagnetic below 200°K. A peak in the susceptibility‐vs‐temperature curve at 310°K indicates a transition from a magnetically ordered arrangement to a paramagnetic one. The effective moment per NpC unit for the ferromagnetic and paramagnetic states is 1.4 μ_B and 3.37 μ_B, respectively.