| 摘要 |
This invention is concerned with the production of transparent glass articles having compositions in the Li2O and/or Na2O-FeO-Al2O3-SiO2 field which additionally contain NiO and/or CoO. Upon exposure to a specifically-defined heat treatment in an oxidizing atmosphere, very fine-grained crystallites of NiFe2O4, CoFe2O4, or (Co,Ni)Fe2O4 are formed spontaneously at the surface of the glass article to produce an integral surface layer thereon having a thickness of not more than about several thousand angstroms. These ferrite surfaces can be magnetized in a strong magnetic field and are relatively easily demagnetized. Such capabilities recommend these surface-crystallized glasses for applications in the storing, recording, retrieving, and erasing of information.
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