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Abstract Some rock and soil samples exhibit significant loss of magnetic susceptibility (χ) with increasing applied field amplitude even at relatively low (10–100s of A/m) fields, a behavior which remains unexplained. Exceptionally strong negative field‐dependence of susceptibility (χHD) is present in sandstones and altered intermediate‐felsic igneous rocks in several cores from the northeastern Oklahoma subsurface. These same rocks also show elevated frequency‐dependence of susceptibility (χFD), with reasonable correlation ofχHDtoχFD, and frequency‐dependentχHD. Results from multiple characterization methods indicate that strongly negativeχHDin these rocks is linked to a yet‐unidentified phase which begins the approach to magnetic saturation in low fields (<1 mT/800 A/m), shows elevatedχFDto low temperatures, is unstable at high temperatures, possesses significant anisotropy of magnetic susceptibility, and becomes paramagnetic above ∼83°C. Clear associations with fluid alteration features indicate that this material may be highly relevant to rock alteration, diagenetic, and environmental studies.
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Role of crystalline and damping anisotropy to the angular dependences of spin rectification effect in single crystal CoFe film
Abstract The angular dependence of the microwave-driven spin rectification (SR) effect in single crystalline Co0.5Fe0.5alloy film is systematically investigated. Due to the strong current-orientation dependent anisotropic magnetoresistance (AMR), the SR effects in CoFe film strongly deviate from the ordinary sin 2φMcosφMrelation withφMdefined as the magnetization angle away from the current. A giant Gilbert damping anisotropy in the CoFe film with a maximum–minimum ratio of 520% is observed, which can impose a strong anisotropy onto magnetic susceptibility. The observed unusual angular dependence can be well explained by the theory including current-orientation dependent AMR and anisotropic magnetic susceptibility. Our work also suggests that the strong current-orientation dependent AMR in single crystalline CoFe film could exist up to the gigahertz frequency range.
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- PAR ID:
- 10303692
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- New Journal of Physics
- Volume:
- 22
- Issue:
- 9
- ISSN:
- 1367-2630
- Page Range / eLocation ID:
- Article No. 093047
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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