Neutron Diffraction Study of Antiferromagnetic Order in the Kondo Compound CePtSn

Abstract

Successive phase transitions in the Kondo compound CePtSn are studied by neutron scattering experiments on a single-crystalline sample. Antiferromagnetic phase transitions are observed at T_N=6.2 K and T_M=3.8 K, which are second and first order transitions, respectively, in accord with the previous specific heat measurement. The magnetic structure is a single-Q type S_nν=a_νe^ik·R_n+a_ν^*e^−ik·R_n with incommensurate modulation vectors k=0.466b^* and 0.418b^* in the low (T<T_M) and intermediate (T_N<T<T_M) temperature phases, respectively. The polarization vectors a_ν cannot uniquely be determined from scattering intensities, and thus those which reproduce the intensities are selected using a maximum entropy method. In the low-temperature phase, the polarization vectors have a, b and c components, and the root mean square of the moment is m_rms=0.84±0.08 μ_B (m_rms^a=0.72, m_rms^b=0.31, m_rms^c=0.29 μ_B) at T=2 K. In the intermediate-temperature phase, the polarization vectors have a and c components, and m_rms=0.60±0.06 μ_B (m_rms^a=0.56, m_rms^c=0.22 μ_B) at T=4.8 K.