Geiger, Charles A., Grodzicki, Michael, Dachs, Edgar (2019) An analysis of the magnetic behavior of olivine and garnet substitutional solid solutions. American Mineralogist, 104 (9) 1246-1255 doi:10.2138/am-2019-6839ccbyncnd
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | An analysis of the magnetic behavior of olivine and garnet substitutional solid solutions | ||
| Journal | American Mineralogist | ||
| Authors | Geiger, Charles A. | Author | |
| Grodzicki, Michael | Author | ||
| Dachs, Edgar | Author | ||
| Year | 2019 (September 1) | Volume | 104 |
| Page(s) | 1246-1255 | Issue | 9 |
| Publisher | Mineralogical Society of America | ||
| DOI | doi:10.2138/am-2019-6839ccbyncndSearch in ResearchGate | ||
| Mindat Ref. ID | 398855 | Long-form Identifier | mindat:1:5:398855:2 |
| GUID | f7e95ac3-90dc-4a33-93e6-af8a2e9b4983 | ||
| Full Reference | Geiger, Charles A., Grodzicki, Michael, Dachs, Edgar (2019) An analysis of the magnetic behavior of olivine and garnet substitutional solid solutions. American Mineralogist, 104 (9) 1246-1255 doi:10.2138/am-2019-6839ccbyncnd | ||
| Plain Text | Geiger, Charles A., Grodzicki, Michael, Dachs, Edgar (2019) An analysis of the magnetic behavior of olivine and garnet substitutional solid solutions. American Mineralogist, 104 (9) 1246-1255 doi:10.2138/am-2019-6839ccbyncnd | ||
| In | (2019, September) American Mineralogist Vol. 104 (9) Mineralogical Society of America | ||
| Abstract/Notes | Abstract The low-temperature magnetic properties and Néel temperature, TN, behavior of four silicate substitutional solid solutions containing paramagnetic ions are analyzed. The four systems are: fayaliteforsterite olivine [Fe22+SiO4-Mg2SiO4], and the garnet series, grossular-andradite [Ca3(Alx,Fe1−x3+)2Si3O12], grossular-spessartine [(Cax,Mn1−x2+)3Al2Si3O12], and almandine-spessartine [(Fex2+,Mn1−x2+)3Al2Si3O12]. Local magnetic behavior of the transition-metal-bearing end-members is taken from published neutron diffraction results and computational studies. TN values are from calorimetric heat capacity, CP, and magnetic susceptibility measurements. These end-members, along with more transition-metal-rich solid solutions, show a paramagnetic to antiferromagnetic phase transition. It is marked by a CP λ-anomaly that decreases in temperature and magnitude with increasing substitution of the diamagnetic component. For olivines, TN varies between 65 and 18 K and TN for the various garnets is less than 12 K. Local magnetic behavior can involve one or more superexchange interactions mediated through oxygen atoms. TN behavior shows a quasi-plateau-like effect for the systems fayalite-forsterite, grossular-andradite, and grossular-spessartine. More transition-metal-rich crystals show a stronger TN dependence compared to transition-metal-poor ones. The latter may possibly show superparamagnetic behavior. (Fex2+,Mn1−x2+)3Al2Si3O12 garnets show fundamentally different magnetic behavior. End-member almandine and spessartine have different and complex interacting local superexchange mechanisms and intermediate compositions show a double-exchange magnetic mechanism. For the latter, TN values show negative deviations from linear interpolated TN values between the end-members. Double exchange seldom occurs in oxides, and this may be the first documentation of this magnetic mechanism in a silicate. TN behavior may possibly be used to better understand the nature of macroscopic thermodynamic functions, CP and S°, of both end-member and substitutional solid-solution phases. | ||
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