Kundu Asish K, Hardy Vincent, Caignaert Vincent, Raveau Bernard
Laboratoire CRISMAT, CNRS ENSICAEN UMR6508, 6 Bd Maréchal Juin, Cedex 4, Caen-14050, France. On leave from Discipline of Physics, Indian Institute of Information Technology, Design & Manufacturing, Dumna Airport Road, Jabalpur-482005, India.
J Phys Condens Matter. 2015 Dec 9;27(48):486001. doi: 10.1088/0953-8984/27/48/486001. Epub 2015 Nov 16.
A new family of oxides in which 3d-3d and 3d-4f interactions are of comparable strength has been synthesized and characterized both from structural and physical viewpoints. These compounds of formulation Ba2LnFeO5 (Ln = Sm, Eu, Gd, Dy, Ho, Er, Yb) are isotypic to the perovskite derivative Ba2YFeO5. They exhibit an original structure consisting of isolated FeO4 tetrahedra linked via LnO6 (or YO6) octahedra. Magnetic and calorimetric measurements show that all these compounds exhibit a unique, antiferromagnetic transition involving both the 3d and 4f ions. The antiferromagnetic properties of the Ln = Y phase (non-magnetic Y(3+)) and of the Ln = Eu (non-magnetic ground state multiplet of Eu(3+)) are ascribed to super-super exchange Fe-O-O-Fe interactions, leading to the lowest T(N) (5.5 K for Y and 4.6 K for Eu). The introduction of a magnetic lanthanide, i.e. Ln = Sm, Gd, Dy, Ho, Er, Yb, in the octahedral sites, leads to larger T(N) values (up to 9.8 K for Ln = Yb). It is found that several mechanisms must be taken into account to explain the complex evolution of the magnetic properties along the Ba2LnFeO5 series. In particular, the super-exchange Ln-O-Fe, as well as the on-site Ln(3+) magnetocrystalline anisotropy, are suggested to play crucial roles. This Ba2LnFeO5 series offers a rare opportunity to investigate experimentally a situation where the 3d-3d and 3d-4f interactions co-operate on an equal footing to trigger a unique long-range magnetic ordering in insulating oxides.
已经合成并从结构和物理角度对一类新型氧化物进行了表征，在这类氧化物中3d-3d和3d-4f相互作用具有相当的强度。这些化学式为Ba2LnFeO5（Ln = Sm、Eu、Gd、Dy、Ho、Er、Yb）的化合物与钙钛矿衍生物Ba2YFeO5同型。它们呈现出一种由通过LnO6（或YO6）八面体相连的孤立FeO4四面体组成的独特结构。磁性和量热测量表明，所有这些化合物都表现出涉及3d和4f离子的独特反铁磁转变。Ln = Y相（非磁性Y(3+)）和Ln = Eu相（Eu(3+)的非磁性基态多重态）的反铁磁特性归因于超超交换Fe-O-O-Fe相互作用，导致最低的奈尔温度T(N)（Y为5.5 K，Eu为4.6 K）。在八面体位点引入磁性镧系元素，即Ln = Sm、Gd、Dy、Ho、Er、Yb，会导致更高的T(N)值（Ln = Yb时高达9.8 K）。发现必须考虑几种机制来解释沿Ba2LnFeO5系列的磁性复杂演变。特别是，超交换Ln-O-Fe以及Ln(3+)的晶场磁晶各向异性被认为起着关键作用。Ba2LnFeO5系列提供了一个难得的机会，通过实验研究3d-3d和3d-4f相互作用在同等基础上协同作用以引发绝缘氧化物中独特的长程磁有序的情况。
