マグネタイトウィスカーからの電界放出電子のスピン偏極度

概要

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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 electron polarimetry. Raising temperature of the whisker to about 120 K, the polarization of field-emitted electrons increased from 4 to 11% with a rotation of its direction. The rotation angle corresponds to a change of magnetic easy axis from 〈001〉 to 〈111〉 direction caused by the Verwey transition. At magnetite temperature of 40 K, the spin polarization was sensitive to increase of the applied field. Eventually, the direction of spin polarization reversed, which can not be explained taking in to account conventional free electron model. These results reveal that the Verwey transition occurs even at a surface as well as in a bulk and that the energy width and level of t2g band become narrower and lower than that of bulk.