对Nd_(1/2)(Sr_(1-x)Ca_x)_(3/2)MnO_4的晶体结构及磁性质的研究

Study of Crystal Structure and Magnetic Properties of Perovskite Manganite Nd_(1/2)(Sr_(1-x)Ca_x)_(3/2)MnO_4

利用固相法制备了Nd1/2(Sr1-xCax)3/2MnO4(x=0.0,0.1,0.3,0.5,0.7,0.8,0.9)系列样品。通过中子衍射确定了系列样品的空间群为四方晶系I4/mmm。发现随着掺杂浓度的升高,电荷有序相变温度随之升高,MnO6八面体面内Mn-O间距与面间Mn-O间距比值减小。对样品Nd1/2(Sr0.3Ca0.7)3/2MnO4的电阻率和磁化率随温度变化关系分别进行了测量,确定其奈尔温度为和电荷有序温度分别为180K和258K。利用可变程跃迁模型,对样品在电荷有序温度之下的电输运特性进行了解释。

Perovskite manganite Ndl/2 （Srl ~ Car ） 3/2 MnO4 （x = 0.0,0.1,0.3,0.5,0.7,0.8,0.9 ） were ob- tained by using solid-state reactions method. Neutron powder diffraction measurements indicate that thus obtained samples were single phase （I4/rnmm, Z：2）. With the increase of x, Tco increases, but the ratio of the out-of-plane Mn-O length of MnO6 octahedra to the in-plane Mn-O length of MnO6 octahedra decrea- ses. In addition, the temperature variation of the susceptibility and the resistivity of Ndl/2 （Sr0.3 Ca0.7 ）3/2 MnO4 were investigated. We have observed that TN ~ 180K and Tco： 258K in Ndl/2 （Sr0.3 Ca0.7 ）3/2 MnO4 , respectively. We interpret the electrical transport properties of Nda/2 （Srl-~Cax）3/2MnO4 below TN in terms of variable range hopping model.