Growth of CaBaCo4O7 single crystal for magnetic order determination

A.L. LARRALDE; E. POMJAKUSHINA; M. KENZELMANN; G. AURELIO; J. CURIALE; J. CAMPO; G. CUELLO; R. SÁNCHEZ

Capital Federal

Congreso; I Congreso Argentino de Técnicas Neutrónicas; 2017

The novel oxide RBaCo4O7, with R=Ca (CBCO-114), is a magnetoelectric compound with the largest magnetic-order induced ferroelectric polarization reported so far (17 mC/m2). It belongs to a family of oxides that display out- standing electronic and magnetic properties, involving magnetic frustration in a three-dimensional framework of Co tetrahedra. CBCO-114 crystallizes in the polar space group P bn21 which allows electric polarization along the c axis. No structural transitions have been observed between 4 K and room temperature, and the compound is believed to have Co3+/Co2+ charge-order.Only a few of the available studies of this material have been performed on single-crystals and no neutron scattering experiments have been reported so far using CBCO-114 crystals. In the framework of a collaboration program between the Paul Scherrer Institut (Switzerland) and the Centro At ́omico Bariloche (Ar- gentina), we synthesized a large single crystal of CaBaCo4O7 with the aim of performing new studies using neutron scattering techniques. One point that re- mains to be addressed is the evolution of the magnetic order with temperature from the paramagnetic state. Despite the textbook arrangement of Co atoms in triangular and Kagom ́e frustrated lattices, the existing orthorhombic distor- tion allows for the development of long-range order. From Neutron Powder Diffraction (NPD) studies, a ferrimagnetic (FiM) phase has been determined which involves a complex non-collinear arrangement of spins. This structure has not been corroborated with single crystal measurements, a more sensitive method for such complex systems. Moreover, the presence of strong AFM cor- relations, that may manifest in short-range order at higher temperatures, has not been studied in CBCO-114, but has been observed by our group using NPD in compounds slightly doped with Sr, as well as other related compounds. Sin- gle crystals will allow to determine the presence and nature of such short-range order and its relation to the reported magnetic structure.In this work, we report the NPD results on Sr-doped CBCO-114 that motivated the single crystal growth and discuss our ongoing efforts to grow and character- ize the single crystals.