Application of Scanning Hall Probe Microscopy for high throughput characterization of combinatorial magnetic materials.

摘要

A Scanning Hall Probe Microscope (SHPM) with a submicron Hall probe (HP) was used for high efficiency characterization of magnetic materials at high magnetic fields. Specifically, we have studied phase diagrams of Co-Fe-Ni binary and ternary alloys, as well as weak itinerant ferromagnet MnSi. The Co-Fe-Ni alloys were fabricated by annealing three metal blocks placed in intimate contact at high temperatures to allow thermal interdiffusion to create solid-solution with a composition spread over the binary and the ternary diffusion regions. The change in the magnetic field in the vicinity of these variable composition diffusion couples and multiples, Fe-Co, Fe-Ni, Co-Ni and Co-Fe-Ni alloys was measured continuously as the HP was scanned across the interdiffusion regions. Using a simple model we have then determined the corresponding saturation magnetizations of the alloys. The values of the saturation magnetization were found to be in good agreement with the known values for pure Fe, Co and Ni. The composition variations and crystal phase structure over the scan regions were measured independently using Energy Dispersive X-ray Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD). Using this technique, the composition-structure-property relationship for the Co-Fe-Ni diffusion system was determined for the first time. This study demonstrates that Scanning Hall microscopy can be used for high efficiency and high accuracy measurements of saturation magnetization and other magnetic properties in variable composition alloys and, in combination with microanalyses techniques, effectively applied to investigations of composition-structure-property relationship and to accelerated design of new magnetic materials. We have also studied the Dzyaloshinskii-Moriya exchange interaction ferromagnet MnSi and investigated its magnetic structure, as it undergoes paramagnetic-helical, helical-conical and conical-ferromagnetic phase transitions.