Chemical pressure induced spin reorientation in the magnetic structure of Ca 3 Mn

Abstract

The effect of partially substituting Tin (Sn) at the Manganese (Mn) site of Ca3Mn2O7 viz. Ca3Mn2-xSnxO7 with x = 0.03 and 0.05, on its structural and magnetic properties has been investigated using synchrotron diffraction, neutron diffraction, and bulk magnetization measurements. It is observed that with a substitution of only 3 at% Sn, the minor (≈ 8%) tetragonal (I4/mmm) structural phase that is present in the predominantly orthorhombic (Cmc21 ) undoped Ca3Mn2O7, completely disappears. The compounds order antiferromagnetically, the ordering temperature decreases with increasing Sn-content, and indicating a weakening of the antiferromagnetic exchange interactions. Interestingly, in the ordered state, the spin magnetic moments which were aligned along the a-axis of the unit cell in the undoped compound, are observed to have reoriented with their major components lying in the b-c plane in the Sn-doped compounds. The above influence of Sn-doping is seen to be stemming from a significant modification of the octahedral rotation and tilt mode geometry in the unit cell, that is known to be responsible for driving ferroelectricity in these compounds.