Anisotropic field-induced melting of orbital ordered structure in Pr0.6Ca0.4MnO3

The magnetic field-dependent transport of Pr0.6Ca0.4MnO3 has been investigated to expose the field-induced melting of orbital ordering. The critical field and critical temperature for the melting of the orbital ordered state depend on the orientation of the applied magnetic field, seemingly independent of the nature of the magnetic phase. The crystalline c axis is the hard axis of the field-induced melting, but in-plane anisotropy also exists, correlating with the anisotropic charge-exchange-(CE) type orbital-ordered structure. These findings demonstrate that the anisotropic melting coincides with the orbital ordering anisotropy, thus indicating a strong spin-orbital coupling.