Reversible and Nonvolatile Modulations of Magnetization Switching Characteristic and Domain Configuration in L10-FePt Films via Nonelectrically Controlled Strain Engineering.

Reversible and nonvolatile modulation of magnetization switching characteristic in ferromagnetic materials is crucial in developing spintronic devices with low power consumption. It is recently discovered that strain engineering can be an active and effective approach in tuning the magnetic/transport properties of thin films. The primary method in strain modulation is via the converse piezoelectric effect of ferroelectrics, which is usually volatile due to the reliance of the required electric field. Also the maximum amount of deformation in ferroelectrics is usually limited to be less than 1%, and the corresponding magnetoelastic strain energy introduced to ferromagnetic films is on the order of 10(4) J/m(3), not enough to overcome magnetocrystalline anisotropy energy (Ku) in many materials. Different from using conventional strain inducing substrates, this paper reports on the significantly large, reversible, and nonvolatile lattice strain in the L10-FePt films (up to 2.18%) using nonelectrically controlled shape memory alloy substrates. Introduced lattice strain can be large enough to effectively affect domain structure and magnetic reversal in FePt. A noticeable decrease of coercivity field by 80% is observed. Moreover, the coercivity field tunability using such substrates is nonvolatile at room temperature and is also reversible due to the characteristics of the shape memory effect. This finding provides an efficient avenue for developing strain assisted spintronic devices such as logic memory device, magnetoresistive random-access memory, and memristor.