Low-temperature magnetism of alabandite: Crucial role of surface oxidation

0397111 - GLÚ 2014 RIV US eng J - Journal Article
Čuda, J. - Kohout, Tomáš - Filip, J. - Tuček, J. - Kosterov, A. - Haloda, J. - Skála, Roman - Santala, E. - Medřík, I. - Zbořil, R.
Low-temperature magnetism of alabandite: Crucial role of surface oxidation.
American Mineralogist. Roč. 98, 8/9 (2013), s. 1550-1556. ISSN 0003-004X. E-ISSN 1945-3027
R&D Projects: GA AV ČR KJB300130903
Institutional support: RVO:67985831
Keywords : alabandite (MnS) * hausmannite (Mn3O4) * magnetism * troilite (FeS) * crystallization * experimental mineralogy * ferromanganese deposit * hysteresis * low temperature * magnetic anomaly * magnetic field * manganese deposit * oxidation * remanent magnetization * stoichiometry * sulfide
Subject RIV: DD - Geochemistry
Impact factor: 2.059, year: 2013

Manganese(II) monosulphide crystallizes into three different polymorphs (α-, β-, and γ-MnS). Out of these, α-MnS, also known as mineral alabandite, is considered the most stable and is widespread in terrestrial materials as well as in extraterrestrial objects such as meteorites. In this study, a low-temperature antiferromagnetic state of α-MnS was investigated using macroscopic magnetic measurements as induced and remanent field-cooled (FC) and zero-field-cooled (ZFC) magnetizations and magnetic hysteresis. Both natural alabandite and synthetic samples show: (1) Néel temperatures in a narrow temperature range around 153 K, and (2) a rapid increase of the magnetization around 40 K. An anomalous magnetic behavior taking place at about 40 K was previously ascribed to the magnetic transition from a high-temperature antiferromagnetic to a low-temperature ferromagnetic state documented for non-stoichiometric α-MnS slightly enriched in manganese. However, our detailed microscopic observations and, in particular, oxidation experiments indicate that the anomalous magnetic behavior around 40 K is caused by the presence of an oxide layer of ferrimagnetic hausmannite (Mn 3O4) on the surface of α-MnS rather than being an intrinsic property of nearly stoichiometric α-MnS.
Permanent Link: http://hdl.handle.net/11104/0224749