Magnetic control of large room-temperature polarization

TL;DR

This paper demonstrates a novel room-temperature multiferroic material that exhibits magnetic control of polarization through a dynamic coupling mechanism, enabling large magnetoelectric effects and multi-state logic capabilities.

Contribution

It introduces a new physical process coupling magnetic and ferroelectric relaxor nano-regions, achieving magnetic switching of polarization at room temperature in a single-phase multiferroic material.

Findings

Achieved magnetic switching between ferroelectric and relaxor states at room temperature.

Observed a large magnetoelectric effect with >5000% capacitance change under magnetic field.

Developed a model linking relaxation time to magnetic field with no adjustable parameters.

Abstract

Numerous authors have referred to room-temperature magnetic switching of large electric polarizations as The Holy Grail of magnetoelectricity.We report this long-sought effect using a new physical process of coupling between magnetic and ferroelectric relaxor nano-regions. Here we report magnetic switching between the normal ferroelectric state and the ferroelectric relaxor state. This gives both a new room-temperature, single-phase, multiferroic magnetoelectric, PbZr0.46Ti0.34Fe0.13W0.07O3, with polarization, loss (<4%), and resistivity (typically 108 -109 ohm.cm) equal to or superior to BiFeO3, and also a new and very large magnetoelectric effect: switching not from +Pr to negative Pr with applied H, but from Pr to zero with applied H of less than a Tesla. This switching of the polarization occurs not because of a conventional magnetically induced phase transition, but because of dynamic effects: Increasing H lengthens the relaxation time by x500 from <200 ns to >100 ?s, and it couples strongly the polarization relaxation and spin relaxations. The diverging polarization relaxation time accurately fits a modified Vogel-Fulcher Equation in which the freezing temperature Tf is replaced by a critical freezing field Hf that is 0.92 positive/negative 0.07 Tesla. This field dependence and the critical field Hc are derived analytically from the spherical random bond random field (SRBRF) model with no adjustable parameters and an E2H2 coupling. This device permits 3-state logic (+Pr,0,negative Pr) and a condenser with >5000% magnetic field change in its capacitance.