论文标题
在绝缘SR $ _ {2-x} $ la $ _x $ conbo $ _6 $中弄清磁相互作用和旋转状态
Unraveling the magnetic interactions and spin state in insulating Sr$_{2-x}$La$_x$CoNbO$_6$
论文作者
论文摘要
我们研究了$ _ {2-x} $ la $ _x $ conbo $ _6 $（$ x = $ x = $ 0--1）double perovskites的结构，磁性和自旋状态过渡和磁性属性。 $ x $ $ \ geqslant $ 0.6的结构过渡到单斜阶段的结构过渡，以及（101）/（103）超级峰值反射和拉曼主动模式的演变表明，B-Site订购的增强量具有$ x $。磁化率数据揭示了从弱铁磁（FM）到反铁磁（AFM）订购的过渡，以$ x $ $ $ \ geqslant $ 0.6 $ _ {\ rm n} $ \ $ 9--15〜K。有趣的是，洛杉矶的替代驱动器朝着更具绝缘状态的状态驱动，这是由于高旋转Co $^{2+} $的增加，而在Co $^{3+} $中观察到了一个自旋状态的跨界，从高旋转到中间/低旋转状态，带有$ x $。我们讨论了复杂磁相互作用与系统中各种CO自旋态的存在之间的相关性。此外，由于FM和AFM相互作用之间的竞争以及从常规磁平衡效应的跨界竞争引起的元磁性质的出现，通过详细分析磁熵的温度和田间依赖性变化，证明了从常规磁平衡效应。
We investigate the structural, magnetic and spin-state transitions, and magnetocaloric properties of Sr$_{2-x}$La$_x$CoNbO$_6$ ($x=$ 0--1) double perovskites. The structural transition from tetragonal to monoclinic phase at $x$ $\geqslant$ 0.6, and an evolution of (101)/(103) superlattice reflections and Raman active modes indicate the enhancement in the B-site ordering with $x$. The magnetic susceptibility data reveal the transition from weak ferromagnetic (FM) to antiferromagnetic (AFM) ordering for $x$ $\geqslant$ 0.6 with T$_{\rm N}$$\approx$9--15~K. Interestingly, the La substitution drives towards more insulating state due to increase in high-spin Co$^{2+}$, whereas a spin-state crossover is observed in Co$^{3+}$ from high-spin to intermediate/low-spin states with $x$. We discuss the correlation between complex magnetic interactions and the presence of various Co spin-states in the system. Moreover, the emergence of metamagnetic nature due to the competition between FM and AFM interactions as well as crossover from conventional to inverse magnetocaloric effect have been demonstrated by detailed analysis of temperature and field dependent change in magnetic entropy.
