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Family of anisotropic spin glassesBa1–xLa1+xMnO4+δ
Physical Review Materials ( IF 3.1 ) Pub Date : 2021-07-09 , DOI: 10.1103/physrevmaterials.5.074403
Mirela Dragomir 1, 2, 3 , Iztok Arčon 4, 5 , Paul A. Dube 2 , Jeremiah C. Beam 6 , Andrew P. Grosvenor 6 , Graham King 7 , John E. Greedan 1, 2
Affiliation  

The synthesis, structural, and magnetic characterization of the series Ba1xLa1+xMnO4+δ (0x0.5) with the K2NiF4-type structure are reported. We previously found that the x=0.2 member exhibits the very rare anisotropic spin-glass behavior with only the c-axis spin component freezing below Tg. Here we show that each member of the Ba1xLa1+xMnO4+δ (0x0.4) series exhibits the same spin-glass behavior. Moreover, Tg varies with x, reaching a maximum of 26.4(4) K for x=0.20 compared with 19.2(2) K for x=0. The spin-glass behavior was confirmed by both dc and ac magnetic susceptibility measurements. No long-range magnetic order was found down to 2 K. All series members adopt the I4/mmm space group and subtle structural transformations occur with increasing La content. The unit cell volume contracts for 0.0<x<0.3 and expands for 0.3<x0.5. Similar behavior is seen for the equatorial Mn-O bonds in the Mn-O octahedron while the axial Mn-O distances increase to x0.3 but remain unchanged for higher x. X-ray absorption near-edge structure analysis revealed that the oxidation state of Mn in the Ba1xLa1+xMnO4+δ samples varies with x: For x0.2 Mn is in the +3.0(1) oxidation state only, while for x>0.2 a mixed +2/+3 oxidation state was found. Therefore, for the charge balance, samples with x0.2 contain excess oxygen as an interstitial species, while for x>0.2, the structure cannot sustain any more interstitial oxygen and the La excess is accommodated through the reduction of some Mn3+ to Mn2+. Based on the oxidation state of Mn, the possible origins of the spin-glass magnetism in the Ba1xLa1+xMnO4+δ series are discussed.

中文翻译:

各向异性自旋玻璃族Ba1–xLa1+xMnO4+δ

该系列的合成、结构和磁性表征 1-X1+X4+δ (0X0.5) 与 2F4-型结构被报告。我们之前发现,X=0.2 成员表现出非常罕见的各向异性自旋玻璃行为,只有 C-轴自旋分量冻结在下方 G. 在这里,我们展示了每个成员1-X1+X4+δ (0X0.4) 系列表现出相同的自旋玻璃行为。而且,GX, 达到最大值 26.4(4) K X=0.20 与 19.2(2) K 相比 X=0. 直流和交流磁化率测量证实了自旋玻璃行为。未发现低至 2 K 的长程磁序。所有系列成员均采用一世4/随着 La 含量的增加,空间群和微妙的结构转变发生。晶胞体积收缩为0.0<X<0.3 并扩展为 0.3<X0.5. 对于 Mn-O 八面体中的赤道 Mn-O 键,可以看到类似的行为,而轴向 Mn-O 距离增加到X0.3 但保持不变为更高 X. X 射线吸收近边结构分析表明,Mn 在1-X1+X4+δ 样本随 X: 为了 X0.2 Mn 仅处于 +3.0(1) 氧化态,而对于 X>0.2发现了混合的 +2/+3 氧化态。因此,对于电荷平衡,样品与X0.2 含有过量的氧作为间隙物质,而对于 X>0.2,该结构不能再承受更多的间隙氧,而过量的 La 通过减少一些 3+2+. 基于 Mn 的氧化态,可能的自旋玻璃磁性起源1-X1+X4+δ 系列进行讨论。
更新日期:2021-07-09
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