Das Manjil, Dutta Prabir, Giri Saurav, Majumdar Subham
School of Physical Sciences, Indian Association for the Cultivation of Science, 2A & B Raja S. C. Mullick Road, Jadavpur, Kolkata 700 032, India.
J Phys Condens Matter. 2019 Sep 25;31(38):385801. doi: 10.1088/1361-648X/ab27f5. Epub 2019 Jun 7.
Rare earth based cobalt-ruthenium double perovskites ACoRuO (A = La, Pr, Nd and Sm) were synthesized and investigated for their structural and magnetic properties. All the compounds crystallize in the monoclinic P2/n structure with the indication of antisite disorder between Co and Ru sites. While La compound is already reported to have an antiferromagnetic state below 27 K, the Pr, Nd and Sm systems are found to be ferrimagnetic below [Formula: see text], 55 and 78 K respectively. Field-dependent magnetization data indicate prominent hysteresis loop below [Formula: see text] in the samples containing magnetic rare-earth ions, however, magnetization does not saturate even at the highest applied fields. Our structural analysis indicates strong distortion in the Co-O-Ru bond angle, as La is replaced by smaller rare-earth ions such as Pr , Nd , and Sm . The observed ferrimagnetism is possibly associated with the enhanced antiferromagnetic superexchange interaction in the Co-O-Ru pathway due to bond bending. The Pr, Nd and Sm samples also show the small magnetocaloric effect with the Nd sample showing the highest value of magnitude ∼3 J kgK at 50 kOe. The change in entropy below 20 K is found to be positive in the Sm sample as compared to the negative value in the Nd counterpart.
合成了基于稀土的钴钌双钙钛矿ACoRuO（A = La、Pr、Nd和Sm），并对其结构和磁性进行了研究。所有化合物均结晶为单斜P2/n结构，表明Co和Ru位点之间存在反位无序。虽然已经报道La化合物在27 K以下具有反铁磁态，但发现Pr、Nd和Sm体系分别在[公式：见原文]、55和78 K以下为亚铁磁性。场依赖磁化数据表明，在含有磁性稀土离子的样品中，在[公式：见原文]以下存在明显的磁滞回线，然而，即使在最高施加场下，磁化也未饱和。我们的结构分析表明，随着La被较小的稀土离子如Pr、Nd和Sm取代，Co-O-Ru键角发生强烈畸变。观察到的亚铁磁性可能与由于键弯曲导致的Co-O-Ru路径中增强的反铁磁超交换相互作用有关。Pr、Nd和Sm样品还表现出小的磁热效应，其中Nd样品在50 kOe时显示出最高的大小值∼3 J kgK。与Nd对应物中的负值相比，发现Sm样品在20 K以下的熵变为正值。
