Titanium substitution has a significant effect on the temperature dependence (5-300 K) of low-temperature saturation remanence and of initial susceptibility in synthetic and natural titanomagnetite (Fe3-x TixO4, 0 ≤ x < 0.7). Our results show that low-temperature magnetic properties of multidomain titanomagnetite are markedly influenced by the temperature dependence of intrinsic anisotropy, including the magnetic effects associated with isotropic points for x < 0.4, rapid temperature changes in the anisotropy constants for x > 0.4, and electronic and lattice relaxation phenomena over the entire titanomagnetite compositional range. These features produce diagnostic magnetic behavior useful for titanomagnetite identification in natural samples. Moreover, the apparent similarities between the thermal decay of low-temperature remanence of titanomagnetite with pyrrhotite, pure magnetite, and superparamagnetic phases can lead to complications in interpreting low-temperature remanence data when titanomagnetite is present.
Bibliographical noteFunding Information:
We thank J.M. Honig, K. Moloni, and J. Rosenbaum for kindly providing us with samples. The authors gratefully acknowledge reviews by Ö. Özdemir and two anonymous reviewers. BMM was partially supported by the National Science Foundation grants EAR-9219621 and EAR-9526812. This is contribution 9702 of the Institute for Rock Magnetism (IRM). The IRM is supported by grants from the Keck Foundation and the NSF. [RV]