Pressure-induced spin and charge transport in La1.25Sr1.75Mn2O7 single crystal

We investigated the effect of uniaxial and hydrostatic pressure on resistivity and ac-magnetic susceptibility of two-dimensional layered manganite, La1.25Sr1.75Mn2O7 (LSMO125) to investigate the lattice effect on magnetic and electronic properties. Asymmetric role of uniaxial pressure, || and ⊥ to c-axis on the spin flop and charge transport has been revealed while comparing hydrostatic pressure. Uniaxial pressure along c-axis increases metal-insulator transition temperature (TMI) and ferromagnetic ordering temperature (TC), whereas it decreases the resistivity along ab-plane (ρab). In contrast to pressure along c-axis, TMI and TC decrease, whereas the resistivity along c-axis (ρc) increases with pressure || to ab-plane. ρc/ρab is quite large, increasing with pressure and shows a peak at around TMI. Uniaxial pressure behaviour is strongly related to the Mn-O-Mn linkage between MnO2 layers and the spin reorientation from the apical axis to the basal plane and vice versa with pressure. Both ρab and ρc decrease whereas TMI and TC increases under hydrostatic pressure. Influence of spin and charge on magnetic and electrical properties under hydrostatic pressure are explained by pressure-induced cant between the MnO2 bilayers and variation in bond lengths. The different pressure driving rates of TMI while measuring ρab and ρc confirms that there is a strong competition between the in and out plane components under hydrostatic pressure.