Applications of Large Strain Near Phase Instabilities in Relaxor Ferroelectric Single Crystals

The biaxial strain produced by relaxor ferroelectric single crystals has has been used extensively to explore the control of magnetism at micron length scales, resulting in many novel applications of the magnetoelectric composite effect. Relaxor ferroelectric single crystals of ternary PIN-PMN-PT undergo electric field and stress driven phase transformations from a rhombohedral phase to an orthorhombic phase when cut, poled, and electrically loaded in the [011]c direction and mechanically loaded in the [001]c direction. At smaller loading levels there is a linear piezoelectric response. At higher loading levels, above the transformation threshold field, there is a considerably larger strain. The threshold field for the phase transformation is a function of composition and temperature. Experimental results of the composition and temperature dependence of the phase transformation threshold are presented. Over the past several years researchers have explored the effect of this strain field on various 2-D shapes with in-plane magnetic anisotropy including rectangular, elliptical, hollow, and full; and recently the effect of this biaxial strain on perpendicular magnetic anisotropy. Multiple examples of controlling magnetism at these length scales are presented. Controlling magnetism at the micron length scale without use of coils enables applications such as capture and release of individual superparamagnetic particles, one of the first steps in a new approach to cell sorting.