Fragile Magnetic Ground State in Half-Doped LaSr(2)Mn(2)O(7)

Abstract

We investigated the orbital and antiferromagnetic ordering behaviors of the half-doped bilayer manganite La2-2xSr1+2xMn2O7 (x similar or equal to 0.5) by using Mn L-2,L-3-edge resonant soft x-ray scattering. Resonant soft x-ray scattering reveals the CE-type orbital order below T-oo similar or equal to 220 K, which shows partial melting behavior below T-m similar or equal to 165 K. We also found coexistence CE- and A-type antiferromagnetic orders. Both orders involve the CE-type orbital order with nearly the same orbital character and are coupled with each other. These results manifest that the ground state with the CE-type antiferromagnetic order is easily susceptible to destabilization into the A-type one even with a small fluctuation of the doping level, as suggested by the extremely narrow magnetic phase boundaries at x similar or equal to 0.5 +/- 0.005.