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Evolution of transition metal charge states in correlation with the structural and magnetic properties in disordered double perovskites Ca2−xLaxFeRuO6 (0.5 ≤ x ≤ 2)
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2021-09-01 , DOI: 10.1039/d1cp02318g
Kumari Naveen 1 , Tanmay Rom 1 , Shams Sohel Islam 2 , Manfred Reehuis 3 , Peter Adler 4 , Claudia Felser 4 , Andreas Hoser 3 , Ramesh Chandra Nath 2 , Ashok Kumar Yadav 5 , Shambhu Nath Jha 5 , Dibyendu Bhattacharyya 5 , Marcus Schmidt 4 , Avijit Kumar Paul 1
Affiliation  

A series of disordered Ca1.5La0.5FeRuO6, CaLaFeRuO6 and La2FeRuO6 double perovskites were prepared by the solid-state reaction method and investigated by neutron powder diffraction, X-ray absorption near-edge structure (XANES) analysis at the Ru–K edge, Mössbauer spectroscopy, DC magnetization and resistivity measurements. All compounds crystallize in the orthorhombic crystal structure with the space group Pbnm down to 3 K, showing a random distribution of Fe and Ru at the B site. Thermogravimetric analysis indicates oxygen deficiency in the Ca-rich and formal oxygen hyperstoichiometry in the La-rich members of the present series. While Mössbauer spectra verify the Fe3+ state for all compositions, the XANES study reveals a variable Run+ oxidation state which decreases with increasing La content. The end member actually is a Ru3+/Ru4+ compound with possibly some cation vacancies. From magnetic susceptibility and neutron diffraction measurements, the presence of a G-type antiferromagnetic ordering was observed with a drastic increase in transition temperature from 275 K (Ca1.5La0.5FeRuO6) to 570 K (La2FeRuO6). Mössbauer spectroscopy confirms the presence of long-range ordering but, due to local variations in the exchange interactions, the magnetic states are microscopically inhomogeneous. All the samples are variable range hopping semiconductors. A complex interplay between structural features, charge states, anion or cation defects, and atomic disorder determines the magnetic properties of the present disordered 3d/4d double perovskite series.

中文翻译:

与无序双钙钛矿 Ca2−xLaxFeRuO6 (0.5 ≤ x ≤ 2) 的结构和磁性相关的过渡金属电荷态的演变

采用固相反应法制备了一系列无序 Ca 1.5 La 0.5 FeRuO 6、CaLaFeRuO 6和 La 2 FeRuO 6双钙钛矿,并通过中子粉末衍射、X射线吸收近边结构(XANES)分析在Ru-K 边缘、穆斯堡尔光谱、直流磁化和电阻率测量。所有化合物都以正交晶体结构结晶,空间群为Pbnm低至 3 K,显示 B 位点处 Fe 和 Ru 的随机分布。热重分析表明本系列的富钙成员中富钙和正式氧超化学计量中的氧缺乏。虽然穆斯堡尔光谱验证了所有成分的 Fe 3+状态,但 XANES 研究揭示了可变的 Ru n +氧化态,随着 La 含量的增加而降低。末端成员实际上是带有可能有一些阳离子空位的 Ru 3+ /Ru 4+化合物。根据磁化率和中子衍射测量,观察到 G 型反铁磁有序的存在,转变温度从 275 K (Ca 1.5 La 0.5FeRuO 6 ) 至 570 K (La 2 FeRuO 6 )。穆斯堡尔光谱证实了长程有序的存在,但由于交换相互作用的局部变化,磁态在微观上是不均匀的。所有样品都是可变范围跳跃半导体。结构特征、电荷态、阴离子或阳离子缺陷以及原子无序之间复杂的相互作用决定了目前无序 3d/4d 双钙钛矿系列的磁性。
更新日期:2021-09-22
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