Rotation of spin-polarization due to the Verwey transition at a surface of a <110>-oriented magnetite whisker observed by field-emitted electrons polarimetry

We observed the Verwey transition, metal-insulator transition, in a spin-polarization of field-emitted electrons from a topmost surface of a <;110>;-oriented magnetite whisker by means of field-emitted electrons polarimetry. The measurements of spin polarization of field-emitted electrons from a magnetite whisker were carried out ranging from 40 to 300 K of tip temperature under UHV condition of 3 × 10^-8 Pa. Raising temperature of the whisker, the polarization increased from 4 to 11 % with a rotation of its direction. The rotation angle corresponds to a change of magnetic easy axis from <;110>; to <;110>; direction caused by the Verwey transition. Our experimental results clarified that the Verwey transition occurs even at a surface as well as in a bulk.