Correlation of magneto-electric coupling with crystal structure in Dy doped hexagonal YMnO3

TL;DR

This study investigates how Dy doping affects the crystal structure, magnetic properties, and magnetoelectric coupling in hexagonal YMnO3, revealing structural modifications and reduced coupling due to Dy-induced strain.

Contribution

It provides a detailed analysis of structural and magnetic changes in Dy-doped YMnO3 and links these to modifications in magnetoelectric coupling, which was not previously characterized.

Findings

Dy doping shrinks the c lattice parameter and expands the ab plane.

Magnetoelectric coupling decreases with Dy doping.

Dy doping reduces the magnetic frustration of Mn lattice.

Abstract

Coexistence of mutually influencing ferroelectric and magnetic ordering at low temperature in hexagonal phase of rare-earth manganites gives rise to interesting physical phenomena. Here, we report a detailed analysis of powder neutron diffraction (ND) studies on polycrystalline Y1-xDyxMnO3 (x = 0, 0.05) as a function of temperature. Our analysis shows that Dy doping at Y site leads to modification in lattice constants: unit cell shrinks in c direction, but expands in ab plane, unit cell volume increases and effective Mn magnetic moment also reduces. All the Mn-O bond lengths and O-Mn-O bond angles shows significant variations leading to reduction in tilting of MnO5 polyhedra. Dielectric measurements on these samples show that, due to Dy doping, inverse S-shape anomaly shifts to the lower temperature side and magnetoelectric coupling decreases. Magnetic measurements confirm the decrease in the frustration of Mn triangular lattice. Temperature dependent specific heat measurement shows anomaly at N\'eel temperature (TN) and results indicate a decrease in entropy due to Dy doping. These results are understood in terms of modification in magnetoelectric coupling triggered due to Dy induced strain in Y plane of YMnO3.