Density functional study of electrode material for magnetic tunnel junction designed using Co2TiZ (Z = Ge, Si) Heusler alloys

Abstract

Some of the important applications in the field of spintronics are spin current driven logic devices having logic gates and in read heads in the hard disk drives, magnetic random access memory (MRAM) containing non-volatile memory units and extremely complex magnetic sensor. In spintronic applications, a magnetic tunnel junction (MTJ) is considered the back bone of all such devices. With this motivation, in present study we have predicted very low resistance area (RA) product value and high tunnel magneto resistance (TMR) of two designed MTJs by using full Heusler alloys (FHA) Co2TiZ (Z = Ge, Si) as electrode and MgO as barrier layer. These used half metallic (HM) Heusler alloys (HA), have been investigated using Wien2K code, via primary standard calculations and studied electronic and magnetic properties followed by structural and magnetic phase stability. Spin based band structure along with density of state (DOS) profiles are determined by considering both generalized gradient approximation (GGA) + modified Becke–Johnson functional (mBJ) functional and GGA potentials. For the estimation of the Curie temperature (Tc) mean field approximation (MFA) was considered. After determining physical properties of considered FHAs, spin polarised transport properties are calculated by using PWCOND code embedded in Quantum ESPRESSO (QE) for designed MTJs and obtained extremely low resistance-area product (RA) product and a high value of TMR which is found very suitable for spintronic device applications.