TY - JOUR
T1 - Magnetic cristobalite (?)
T2 - A possible new magnetic phase produced by the thermal decomposition of nontronite
AU - Moskowitz, Bruce M.
AU - Hargraves, Robert B.
PY - 1984
Y1 - 1984
N2 - Prolonged heat treatment (>1 hour) of nontronite (an iron-rich smectite clay) at 900° to 1000°C produces a phase with some unusual magnetic properties. This new phase has a Curie temperature of 200° to 220°C, extremely high remanent coercivities in excess of 800 milliteslas, and a room-temperature coercivity dependent on the magnitude of the applied field during previous thermomagnetic cycling from above 220°C. X-ray and magnetic analyses suggest that an iron-substituted cristobalite could be responsible, in part, for these observations. Formation of this magnetic cristobalite, however, may require topotactic growth from a smectite precursor.
AB - Prolonged heat treatment (>1 hour) of nontronite (an iron-rich smectite clay) at 900° to 1000°C produces a phase with some unusual magnetic properties. This new phase has a Curie temperature of 200° to 220°C, extremely high remanent coercivities in excess of 800 milliteslas, and a room-temperature coercivity dependent on the magnitude of the applied field during previous thermomagnetic cycling from above 220°C. X-ray and magnetic analyses suggest that an iron-substituted cristobalite could be responsible, in part, for these observations. Formation of this magnetic cristobalite, however, may require topotactic growth from a smectite precursor.
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U2 - 10.1126/science.225.4667.1152
DO - 10.1126/science.225.4667.1152
M3 - Article
AN - SCOPUS:0021638797
SN - 0036-8075
VL - 225
SP - 1152
EP - 1154
JO - Science
JF - Science
IS - 4667
ER -