Semeno A V, Anisimov M A, Bogach A V, Demishev S V, Gilmanov M I, Filipov V B, Shitsevalova N Yu, Glushkov V V
Prokhorov General Physics Institute of the Russian Academy of Sciences, Vavilov str. 38, Moscow, 119991, Russia.
National Research University Higher School of Economics, Myasnitskaya str. 20, Moscow, 101000, Russia.
Sci Rep. 2020 Oct 26;10(1):18214. doi: 10.1038/s41598-020-75327-8.
Randomness and frustration are believed to be two crucial criteria for the formation of spin glass state. However, the spin freezing occurs in some well-ordered crystals below the related temperature T due to the instability of each spin state, which induces the variation of either magnetic moment value or exchange energy. Here we explore the new mechanism of the in-site originated disorder in antiferromagnets GdLaB and GdB, which is caused by the random mutual shifts of Gd spins from the centrally symmetrical positions in the regular cubic lattice. The universal scaling of ESR linewidth temperature dependencies to the power law ΔH(T) ~ ((T - T)/T) with α = - 1.1 ± 0.05 in the paramagnetic phase of both compounds demonstrates the identity of the origin of magnetic randomness. In GdLaB the resulting random spin configurations freeze at T ≈ 10.5 K where the maximum of magnetization is observed. Below T the splitting of ZFC and FC magnetization curves takes place as well as the magnetic state depends on the antecedent sample history. In the case of GdB the coherent displacement of Gd ions compete with these random shifts forming an antiferromagnetic (AFM) phase at T = 15.5 K, which prevails over the spin freezing at T ≈ 13 K, expected from the ESR data. The observation of the hysteresis of the ESR spectrum in the AFM phase suggests that its properties may be determined by the competition of two types of AFM orders, which results in formation of stable magnetic domains with nonequivalent positions of AFM Gd pairs at T < 10 K.
随机性和受挫被认为是形成自旋玻璃态的两个关键标准。然而，由于每个自旋态的不稳定性，在低于相关温度T时，一些有序晶体中会发生自旋冻结，这会导致磁矩值或交换能的变化。在这里，我们探索反铁磁体GdLaB和GdB中由内禀无序引起的新机制，这是由Gd自旋在规则立方晶格中从中心对称位置的随机相互位移所导致的。两种化合物顺磁相中的电子自旋共振（ESR）线宽温度依赖性与幂律ΔH(T) ~ ((T - T)/T)（α = - 1.1 ± 0.05）的普遍标度表明了磁随机性起源的一致性。在GdLaB中，产生的随机自旋构型在T ≈ 10.5 K时冻结，此时观察到磁化强度的最大值。在T以下，零场冷却（ZFC）和场冷却（FC）磁化曲线发生分裂，并且磁状态取决于先前的样品历史。在GdB的情况下，Gd离子的相干位移与这些随机位移相互竞争，在T = 15.5 K时形成反铁磁（AFM）相，该相在T ≈ 13 K时的自旋冻结之上占主导地位，这是根据ESR数据所预期的。在AFM相中观察到ESR谱的磁滞现象，这表明其性质可能由两种类型的AFM序的竞争所决定，这导致在T < 10 K时形成具有AFM Gd对不等价位置的稳定磁畴。
