Full text loading...
Azimuthally-averaged total SANS cross section of as a function of momentum transfer q and applied magnetic field H (T = 300 K). Solid circles (•): H values (in Tesla) decrease from bottom to top: 10, 6, 1, −0.25, −0.55; ( ): −1 T; ( ): −3 T. Inset: Room-temperature magnetization curve of .
Applied-field dependence of the spin-misalignment SANS cross section of nanocrystalline (T = 300 K). Solid circles (•): H values (in Tesla) decrease from bottom to top: 6, 1, −0.25, −0.55; ( ): −1 T; ( ): −3 T. Dashed line: .
(a) Field dependence of the correlation function C(r) of the spin misalignment of nanocrystalline (semi-logarithmic scale). The field values follow the course of a hysteresis loop, starting from a large positive field and then reducing the field to negative values. Dotted line (extrapolating the 6 T data to r = 0): C(r) = 4.58 − 0.043 . (b) Field dependence of the spin-misalignment length . Solid line: fit of the data to , where and aretreated as adjustable parameters; the quantities A = 12.5 pJ/m and are held fixed. For comparison, data obtained at the SANS instruments KWS 1 (JCNS, Germany) and D11 (ILL, France) are included. Dashed horizontal line: average particle radius R = 11 nm. Dotted vertical line: experimental coercive field . Inset: Sketch illustrating the meaning of . In the presence of an applied magnetic field H, the magnetization of the particle may be tilted away from the strong uniaxial anisotropy axis of the particle. The jump in the materials parameters at the “hard-soft” interface (here, predominantly fluctuations) gives rise to spin disorder that is transmitted via the exchange interaction (on a decay length ) into the soft magnetic crystallites.
Article metrics loading...