Visualization of Melting of Antiferromagnetic Insulator Phase in Phase-Separated Manganite Film using Magnetic Force Microscopy

Abstract

The phase separation and magnetic-field-induced transition of the antiferromagnetic charge-ordered insulator (AFI) phase into the ferromagnetic metal (FM) phase in an anisotropically-strained manganite thin film is directly imaged using a home-built magnetic force microscope (MFM). The MFM images at 10 K show that the two competing phases already coexist in zero magnetic field. Remarkably anisotropic distribution of the stripe-like phase domains are observed, which can qualitatively account for the anisotropic transport. Above 2.2 T, the AFI phase starts to transform into FM phase gradually. The melting of AFI phase is completed at 3.2 T. The FM phase can be retained after the magnetic field is removed, suggesting the metastable nature of the AFI phase at this temperature.