Magnetoelectric behavior via a spin state transition

Shalinee Chikara,Brian Scott,John Singleton,Hai-Ping Cheng,Nathan Smythe,X.-G Zhang,Jim Eckert,Vivien S Zapf,Jie Gu,Elizabeth Krenkel

doi:10.1038/s41467-019-11967-3

Abstract

In magnetoelectric materials, magnetic and dielectric/ferroelectric properties couple to each other. This coupling could enable lower power consumption and new functionalities in devices such as sensors, memories and transducers, since voltages instead of electric currents are sensing and controlling the magnetic state. We explore a different approach to magnetoelectric coupling in which we use the magnetic spin state instead of the more traditional ferro or antiferromagnetic order to couple to electric properties. In our molecular compound, magnetic field induces a spin crossover from the S = 1 to the S = 2 state of Mn3+, which in turn generates molecular distortions and electric dipoles. These dipoles couple to the magnetic easy axis, and form different polar, antipolar and paraelectric phases vs magnetic field and temperature. Spin crossover compounds are a large class of materials where the spin state can modify the structure, and here we demonstrate that this is a route to magnetoelectric coupling.

Highlights

In magnetoelectric materials, magnetic and dielectric/ferroelectric properties couple to each other
In this work we explore whether an state transitions (SSTs) can toggle electric polarization and thereby create magnetoelectric coupling
To extract equilibrium experimental properties we used quasi-DC magnets up to 14T to measure magnetization, dielectric constant and heat capacity, and quasi-DC magnets up to 45T to measure the change in electric polarization, ΔP (H, T) and dielectric constants Δε′ðH; TÞ

Summary

Introduction

Magnetic and dielectric/ferroelectric properties couple to each other. Magnetic field induces a spin crossover from the S = 1 to the S = 2 state of Mn3+, which in turn generates molecular distortions and electric dipoles. These dipoles couple to the magnetic easy axis, and form different polar, antipolar and paraelectric phases vs magnetic field and temperature. In the HS state, dynamic Jahn-Teller (JT) distortions[29,34,35] deform the molecules such that they contain an additional electric dipole component that is perpendicular to the trigonal axis This distortion can occur in three different nearly degenerate ways, creating three directions for the HS dipole. The scenario described above has emerged from measurements of X-

Methods

Results

Conclusion