Dimorphic Nd2Cu2Cd - structures and magnetic properties of RE2Cu2Cd (RE = Ce, Pr, Nd)

作者：Tappe Frank; Hoffmann Rolf Dieter; Eul Matthias; Poettgen Rainer

来源：Zeitschrift fur Kristallographie-Crystalline Materials, 2011, 226(3): 201-213.

DOI：10.1524/zkri.2011.1297

• Intermetallics
• Superstructure
• Group-subgroup
• Magnetic properties
• Phase transition

The intermetallic compounds RE2Cu2Cd (RE = Ce, Fr, Nd) were synthesized by induction-melting of the, elements. Nd2Cu2Cd is dimorphic with a tetragonal Mo2B2Fe high- (HT) and a monoclinic, Mn2B2Al related low-temperature (LT) modification. The reconstructive phase transition is confirmed by DTA measurements showing a fully reversible phase transition commencing around 931(2) K. Both structures were refined on the basis of single crystal X-ray diffractometer data: P4/mbm, a = 764.7(3), c = 385.3(2) pm, wR2 = 0.0529, 288 F-2 values, 12 variables for HT-Nd2Cu2Cd and C2/c, a = 847.6(2), b = 740.4(2), c = 1509.3(5) pm, beta = 106.31(2)degrees, 1180 F-2 values, 48 variables for LT-Nd2Cu2Cd. Both modifications are simple 1:1 intergrowth variants with slightly distorted CsCl and AlB2 related slabs of compositions NdCd and NdCu2. Formation of the monoclinic superstructure is discussed on the basis of a group sub-group scheme. Monoclinic Ce2Cu2Cd (a = 859.1(s), b = 743.0(3), c = 1520.6(7) pm, beta = 106.37(5)degrees, 1243 F-2 values, 48 variables) and Pr2Cu2Cd (a = 855.8(4), b = 742.1(3), c = 1519.7(5) pm, beta = 106.35(3)degrees, 1238 F-2 values, 48 variables) crystallize directly from the melt. Ce2Cu2Cd, Pr2Cu2Cd, LT- and HT-Nd2Cu2Cd show Curie-Weiss paramagnetism and magnetic ordering at low temperatures.

• 出版日期2011