Technical Report of ISSP Ser. A: Number 2747

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(sub N) = 6.2 K and T(sub 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(sub nv) = a(sub v) e(exp ikR(sub n)) + a(sup *)(sub v) e(exp -ikR(sub n)) with incommensurate modulation vectors k = 0.466b(sup *) and 0.418b(sup *) in the low (T less than T(sub M)) and intermediate (T(sub N) less than T less than T(sub M)) temperature phases, respectively. The polarization vectors a(sub v) 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(sub rms) = 0.84 +/- 0.08 micron(sub B) (m(sup a)(sub rms) = 0.72, m(sup b)(sub rms) = 0.31, m(sup c)(sub rms) = 0.29 micron(sub B)) at T = 2K. In the intermediate-temperature phase, the polarization vectors have a and c components, and m(sub rms) = 0.60 +/- 0.06 micron(sub B) (m(sup a)(sub rms) = 0.56, m(sup c)(sub rms) = 0.22 micron(sub B)) at T = 4.8 K

近藤化合物CePtSnの逐次相転移を単結晶について中性子散乱実験により調べた。TN=6.2KおよびTM=3.8Kにおいて反強磁性相転移が観測されたが、それらはそれぞれ、2次および1次相転移であり、以前の比熱測定結果と一致していた。磁気構造は、それぞれ低温(T＜TM)および中温(TM＜T＜TN)相において非整合変調ベクトルK=0.466b｛*｝および0.418｛b*｝を持つ単一Q型SN(nv)=ave(ik・Rn｝+av｛*｝e｛-ik・Rn｝を示した。分極ベクトルavは散乱実験からはユニークに決定することができず、強度を再現するこれら分極ベクトルは最大エントロピー法を用いて選択された。低温相において、分極ベクトルはa,bおよびc成分を持ち、モーメントの平方根2乗平均はT=2Kにおいてmvms=0.84±0.08μB(mrms｛a｝=0.72、mrms｛b｝=0.31、mrms｛c｝=0.29μB)を示した。中温相においては、分極ベクトルはaおよびc成分を持ち、T=4.8Kにおいてmrms=0.60±0.06μB(mrms｛a｝=0.56、mrms｛c｝=0.22μB)を示した。