Magnetic Structures of the Rare-Earth Platinum AluminidesRPtAl (R=Ce, Pr, Nd)
Magnetic Structures of the Rare-Earth Platinum AluminidesRPtAl (R=Ce, Pr, Nd)
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稀土铂铝化物RPtAl (R=Ce, Pr, Nd) 的磁性结构
DOI：
10.1006/jssc.1998.7881
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发表时间：
1998
影响因子：
5.4
通讯作者：
G. Kido
中科院分区：
文献类型：
--
作者：
H. Kitazawa;A. Donni;L. Keller;J. Tang;F. Fauth;G. Kido
稀土铂铝化合物RPtAl具有正交TiNiSi型结构（空间群Pnma，Z=4），磁性稀土原子形成平行于a轴和平行于b轴的链状网络。通过对多晶样品的磁化率、比热和中子衍射的系统测量，研究了RPtAl（R=Ce，Pr，Nd）化合物的磁结构和相变。结果表明，样品具有较大的磁晶各向异性和磁结构，其中平行于两个链方向之一的铁磁成分占主导地位：CePtAl和PrPtAl的a轴，NdPtAl的b轴。CePtAl具有三个连续的磁相变（TC= 5.9K，T2= 4.3K，T3= 2.5K）和两个共存的传播矢量（对于T ≤TC，k1=0;对于T2 ≤T≤TC，k2=[0，0.46，0]; PrPtAl具有与第一激发态CEF单重态相距21 K的双晶电场（CEF）基态单重态，且磁交换作用足够强，可诱导出长程磁有序（居里温度TC =5.8 K，传播矢量k1=0，磁群Pnm′a′，有序饱和磁矩m1 =1.00（7）μB）. NdPtAl是简单铁磁体（TC= 19.2K，k1=0，Pn′ma′，m1=2.08（4）μB）。
Abstract The rare-earth (R) platinum aluminidesRPtAl crystallize in the orthorhombic TiNiSi-type structure (space group Pnma,Z=4), where magnetic rare-earth atoms form a network of chains parallel to thea-axis and parallel to theb-axis. Magnetic structures and phase transitions ofRPtAl (R=Ce, Pr, Nd) compounds were investigated by systematic measurements of magnetic susceptibility, specific heat, and neutron diffraction on polycrystalline samples. The results reveal a large magnetocrystalline anisotropy and magnetic structures that are dominated by a ferromagnetic component parallel to one of the two chain directions: thea-axis for CePtAl and PrPtAl and theb-axis for NdPtAl. The complex magnetism of CePtAl with three successive magnetic phase transitions (TC=5.9 K,T2=4.3 K,T3=2.5 K) and two coexisting propagation vectors (k1=0 forT≤TC, k2i=[0, 0.46, 0] forT2≤T≤TC, k2=[0, 1/2, 0] forT≤T2) is confirmed to be exceptional amongRPtAl compounds. PrPtAl has a nonmagnetic crystalline-electric field (CEF) ground-state singlet separated by 21 K from the first-excited state CEF singlet and magnetic exchange interactions are strong enough to induce long-range magnetic order (Curie temperatureTC=5.8 K, propagation vector k1=0, magnetic group Pnm′a′, ordered saturation momentm1=1.00(7)μB). NdPtAl is a simple ferromagnet (TC=19.2 K, k1=0, Pn′ma′,m1=2.08(4)μB).