Magnetic Phase Diagrams of Multiferroic Hexagonal RMnO3 (R=Er, Yb, Tm, and Ho)

TL;DR

This study maps the magnetic phase diagrams of hexagonal RMnO3 (R=Er, Yb, Tm, Ho) up to 14 Tesla, revealing extended AFM stability, spin-lattice coupling, and magnetoelastic effects through magnetic, dielectric, and magnetostriction measurements.

Contribution

It provides detailed magnetic phase diagrams of RMnO3 compounds up to high magnetic fields, highlighting strong spin-lattice interactions and magnetoelastic effects.

Findings

AFM order persists at higher fields than previously thought

Strong spin-lattice coupling evidenced by dielectric anomalies

Magnetostriction reveals significant magnetoelastic distortions in HoMnO3

Abstract

The magnetic phase diagrams of RMnO3 (R = Er, Yb, Tm, Ho) are investigated up to 14 Tesla via magnetic and dielectric measurements. The stability range of the AFM order below the Neel temperature of the studied RMnO3 extends to far higher magnetic fields than previously assumed. Magnetic irreversibility indicating the presence of a spontaneous magnetic moment is found near 50 K for R=Er, Yb, and Tm. At very low temperatures and low magnetic fields the phase boundary defined by the ordering of the rare earth moments is resolved. The sizable dielectric anomalies observed along all phase boundaries are evidence for strong spin-lattice coupling in the hexagonal RMnO3. In HoMnO3 the strong magnetoelastic distortions are investigated in more detail via magnetostriction experiments up to 14 Tesla. The results are discussed based on existing data on magnetic symmetries and the interactions between the Mn-spins, the rare earth moments, and the lattice.