| Summary: | 碩士 === 國立清華大學 === 物理學系 === 97 === Multiferroics are materials that exhibit more than one primary ferroic order parameter
in single phase. A special kind of multiferroics with a gigantic magnetoelectric coupling has attracted much attention. Haxeferrite Ba2Mg2Fe12O22 is a particularly interesting magnetoelectric material because its electric polarization can be controlled by a low magnetic field. However, such a multiferroic feature is far from being understood. We here investigated magnetic properties and transitions of Ba2Mg2Fe12O22 by using a superconducting quantum interference device (SQUID), soft x-ray absorption including magnetic circular dichroism, and resonant soft x-ray magnetic scattering. The results indicate that Ba2Mg2Fe12O22 exhibits an anisotropic spin ordering and a commensurate-to-incommensurate magnetic transition. Two-dimension distributions of magnetic scattering reveal a weak spin-spin correlation along the c axis, leading to a possible scenario for the low-field control of electric polarization discovered in haxeferrite Ba2Mg2Fe12O22.
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