Extremely strong anisotropy of out-of-phase component of AC magnetic susceptibility in hematite single crystals and its origin

0561314 - GLÚ 2023 RIV CZ eng J - Článek v odborném periodiku
Hrouda, F. - Ježek, J. - Chadima, Martin
Extremely strong anisotropy of out-of-phase component of AC magnetic susceptibility in hematite single crystals and its origin.
Studia geophysica et geodaetica. Roč. 66, 3-4 (2022), s. 187-205. ISSN 0039-3169. E-ISSN 1573-1626
Institucionální podpora: RVO:67985831
Klíčová slova: out-of-phase susceptibility * hematite * single crystals
Obor OECD: Condensed matter physics (including formerly solid state physics, supercond.)
Impakt faktor: 0.9, rok: 2022
Způsob publikování: Omezený přístup
https://link.springer.com/article/10.1007/s11200-022-0829-2

So far unknown anisotropic properties of out-of-phase magnetic susceptibility (opMS) of hematite and their bearing on understanding the origin of hematite magnetism were investigated on example of four single crystals from Minas Gerais, Brazil. The research comprised measurement of directional variation of field-dependent and frequency-dependent opMS and testing whether the anisotropy of opMS can be represented by the second rank tensor. It was found that the opMS shows strong field dependence along basal plane and only weak field dependence along c-axis. As for the frequency dependence, it is virtually non-existent along the basal plane. Along the c-axis, the opMS is similar at frequencies 976 and 3904 Hz, while at 15616 Hz it is clearly higher. Consequently, opMS is dominantly due to weak field hysteresis. The minimum opMS directions are parallel to the c-axis, while the other two principal directions lie within basal plane. The degree of anisotropy is extremely high (ratio of maximum opMS to minimum opMS ≫100) and the anisotropy ellipsoid is very oblate. In stereographic diagrams, the opMS contours very roughly resemble the theoretical contours calculated from opMS tensor. However, the differences between measured and theoretical values in directional opMS are clearly higher than the measuring error and are distributed very non-homogeneously. This indicates that the second rank tensor is only very approximate representative of the spatial variation of the directional opMS of hematite single crystals. Earlier model of hematite magnetism assuming slightly scanted antiferromagnetism along the c-axis and strongly canted antiferromagnetism or even weak ferromagnetism along the basal plane is supported.
Trvalý link: https://hdl.handle.net/11104/0335779