Spin-ordering and magnetoelastic coupling in the extended Kagome system YBaCo4O7

TL;DR

This study investigates the low-temperature magnetic and structural properties of YBaCo4O7, revealing a structural transition and magnetic ordering driven by strong magnetoelastic coupling, with detailed models of magnetic structures at different temperatures.

Contribution

It provides new insights into the spin-ordering and magnetoelastic coupling mechanisms in the extended Kagome system YBaCo4O7, including detailed magnetic structure models.

Findings

Structural transition from orthorhombic to monoclinic at ~100 K

Magnetic ordering associated with the structural transition

Additional magnetic transition at ~60 K with iso-symmetric change

Abstract

Low temperature magnetic and structural behavior of the extended Kagome system YBaCo4O7 has been studied by single crystal neutron diffraction and high-resolution powder X-ray diffraction. Long-range magnetic ordering associated with a structural transition from orthorhombic Pbn2_1 to monoclinic P2_1 symmetry has been found at T_1 ~ 100 K. The interplay between the structural and magnetic degrees of freedom testifies that the degeneracy of the magnetic ground state, present in the orthorhombic phase, is lifted through a strong magnetoelastic coupling, as observed in other frustrated systems. At T_2 ~ 60 K, an additional magnetic transition is observed, though iso-symmetric. Models for the magnetic structures below T_1 and T_2 are presented, based on refinements using a large number of independent reflections. The results obtained are compared with previous single crystal and powder diffraction studies on this and related compositions.