Jena Suchit Kumar, Sarkar Tapati, RoyChowdhury Mouli, Weise Bruno, Qi Yajun, Thota Subhash
Department of Physics, Indian Institute of Technology, Guwahati 781039, Assam, India.
Department of Materials Science and Engineering, Uppsala University, SE-75103 Uppsala, Sweden.
J Phys Condens Matter. 2022 Aug 3;34(40). doi: 10.1088/1361-648X/ac8329.
We report the slow spin dynamics of cluster spin-glass (SG) spinel Zn(Fe1-xRu)Oby means of detaileddc-magnetization andac-susceptibility studies combined with the heat capacity analysis. Two specific compositions ( = 0.5, 0.75) have been investigated in detail along with the substitution of Jahn-Teller (JT) active spin-1/2 Cuions at B-sites. Measurements based on the frequency and temperature dependence ofac-susceptibility (χac(f,T)) and the subsequent analysis using the empirical scaling laws such as: (a) Vogel-Fulcher law and (b) Power law reveal the presence of cluster SG state below the characteristic freezing temperatureTSG(17.77 K ( = 0.5) and 14 K ( = 0.75)). Relaxation dynamics of both the compositions follow the non-mean field de Almeida-Thouless (AT)-line approach(TSG(H)=TSG(0)(1-AH2/ϕ)), with an ideal value of = 3. Nevertheless, the analysis of temperature dependent high fielddc-susceptibility,χhf(2kOe ⩽ HDC ⩽ 20kOe,) provides evidence for Gabay-Toulouse type mixed-phase (coexistence of SG and ferrimagnetic (FiM)) behaviour. Further, in the case of CuZnFeRuOsystem, slowly fluctuating magnetic clusters persist even above the short-range FiM ordering temperature (TFiM) and their volume fraction vanishes completely across ∼6TFiM. This particular feature of the dynamics has been very well supported by the time decay of the thermoremanent magnetization and heat-capacity studies. We employed the high temperature series expansion technique to determine the symmetric exchange coupling (JS) between the spins which yieldsJS=-3.02×10-5 eV for CuZnFeRuOrepresenting the dominant intra-sublattice ferromagnetic interactions due to the dilute incorporation of the JT active Cuions. However, the antiferromagnetic coupling is predominant in ZnFeRuOand CuZnFeRuOsystems. Finally, we deduced the magnetic phase diagram in theHDC-Tplane using the characteristic parameters obtained from the field variations of bothac- anddc-magnetization measurements.
我们通过详细的直流磁化和交流磁化率研究，并结合热容量分析，报道了团簇自旋玻璃（SG）尖晶石Zn(Fe1-xRu)O的缓慢自旋动力学。我们详细研究了两个特定成分（x = 0.5, 0.75），并在B位用Jahn-Teller（JT）活性自旋1/2 Cu离子进行了替代。基于交流磁化率（χac(f,T)）的频率和温度依赖性的测量，以及随后使用经验标度律（如：（a）Vogel-Fulcher定律和（b）幂律）进行的分析表明，在特征冻结温度TSG（x = 0.5时为17.77 K，x = 0.75时为14 K）以下存在团簇SG态。两种成分的弛豫动力学都遵循非平均场德阿尔梅达 - 图勒斯（AT）线方法（TSG(H)=TSG(0)(1 - AH2/ϕ)），理想值ϕ = 3。然而，对温度依赖的高场直流磁化率χhf(2kOe ⩽ HDC ⩽ 20kOe)的分析提供了加贝 - 图卢兹型混合相（SG和亚铁磁（FiM）共存）行为的证据。此外，在CuZnFeRuO系统中，即使在短程FiM有序温度（TFiM）以上，缓慢波动的磁团簇仍然存在，并且它们的体积分数在约6TFiM时完全消失。热剩余磁化的时间衰减和热容量研究很好地支持了这种动力学的特殊特征。我们采用高温级数展开技术来确定自旋之间的对称交换耦合（JS），对于CuZnFeRuO，得到JS = -3.02×10-5 eV，这代表了由于JT活性Cu离子的稀释掺入而导致的主要亚晶格内铁磁相互作用。然而，在ZnFeRuO和CuZnFeRuO系统中反铁磁耦合占主导。最后，我们利用从交流和直流磁化测量的场变化中获得的特征参数，推导出了HDC - T平面中的磁相图。
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