- journal_title：American Mineralogist
- Contributor：Jan Čuda ; Tomáš Kohout ; Jan Filip ; Jiří Tuček ; Andrei Kosterov ; Jakub Haloda ; Roman Skála ; Eero Santala ; Ivo Medřík ; Radek Zbořil
- Publisher：Mineralogical Society of America
- Date：2013-08-01
- Format：text/html
- Language：en
- Identifier：10.2138/am.2013.4348
- journal_abbrev：American Mineralogist
- issn：0003-004X
- volume：98
- issue：8-9
- firstpage：1550
- section：Articles
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 (Mn3O4) on the surface of α-MnS rather than being an intrinsic property of nearly stoichiometric α-MnS.