Even Odd Oscillation in Tunnelling Magneto Resistance of Transition metal doped Metallo Porphyrin systems

Abstract

Abstract Herein we report variation in Tunnelling magneto resistance (TMR) of TM-porphyrin against increase in d electrons from n=1 to 8; as the transition metal changes across the periodic table from Sc to Ni. We observed that highest value of TMR is observed for d5 system the TMR becomes gigantic (1022) at the equilibrium and on either side of it we need to apply certain amount of energy to reach appreciable TMR. An even-odd oscillation of TMR is observed against the number of electrons in d orbital. We also observed that with even number of d electrons TMR values is on lower side and in many cases below the accepted range (150%) of an efficient TMR device. In fact, to achieve an acceptable range we need to apply relatively larger energy (as large as 0.7 eV for Ni) probably due to preference of low spin states in presence of even number of electrons in an atom. Observed feature has been explained using molecular orbital obtained in each case.