Spin-Wave Excitations and Fluctuations of the Exchange Interaction in Amorphous Fe_1-xZr_xAlloys

Abstract

Detailed magnetization measurements were performed on amorphous F e 1 -x Z r x a l l o y s w i t h 0 . 1 4 < x < 0 . 4 8 a t t e m p e r a t u r e s r a n g i n g f r o m 4 . 2 K t o the Curie temperature in external magnetic field up to 5 T. An analysis of the experimental data reveals that' the fluctuations of the exchange integral resulting froni the structural disorder give important contribution to the thermal demagnetization and high-field susceptibility of Fe-rich alloys. For Zr-rich alloys the effect of fluctuations of the exchange integral is negligible and thermal demagnetization is described in terms of spin-wave excitations.No Stoner single-particle excitations were observed for alloys with x > 0.14.

Low-field magnetization of radio-frequency-sputtered amorphous alloys: the magnetic phase diagram

“…This communication is the latest in a series of reports on the same Fe x Zr 100−x rfsputtered amorphous samples involving magnetic properties [17], anomalous Hall effect measurements [27], electrical resistivity [28] and Mössbauer measurements [26]. Our aim is to explore the variation of the magnetic structure with composition in a way which can help to distinguish between the two proposed models, and allow a magnetic phase diagram to be proposed.…”

“…Magnetization measurements have been reported on rf-sputtered Fe x Zr 100−x amorphous samples [3,17] within the intermediate-concentration range (35 x 85). These results show a very large high-field susceptibility for all samples, and that the contributions to the thermal demagnetization are determined only by spin-wave excitations and not by fluctuation of the exchange integral, as in the Fe-rich region.…”

Structural and magnetic properties of amorphous Fe/Zr multilayers

“…The constraints imposed by the modulated structure on the spin structure are probably responsible for the reduction in the high-field susceptibility (homogeneous amorphous Fe-Zr alloys cannot be saturated with fields of 5 T [35]). Our previous CEMS measurements in polycrystalline Fe/Zr multilayers [24] show an in-plane direction of the magnetic moments, so one could infer that the canting of the magnetic moments in the Fe 2 Zr amorphous layers may be reduced as compared with intrinsic canting of homogeneous rf-sputtered amorphous Fe 2 Zr alloy, and this indeed appears to be the case.…”

“…The disappearance of coercivity at low temperatures is not related to the temperatures where this splitting occurs giving evidence [34] for the asperomagnetic behaviour of these two samples. The high-field susceptibility appears to be low as compared with homogeneous Fe 2 Zr amorphous alloys [25,35] and both samples are saturated at fields around 1 T. Figure 5 shows a displaced hysteresis loop at 5 K when sample 3/6 Å was cooled down in a negative field of −100 mT. This behaviour is a characteristic feature of spin-glass-like amorphous systems [36].…”

Magnetohydrodynamic instabilities in a self-gravitating rotating cosmic plasma

“…To mention a few of them, Prajapati et al [14] have investigated the self-gravitational instability in anisotropic rotating plasmas and showed that the effects of rotation can stabilize the system. Kossacki [15] studied the Jeans instability in viscous plasmas with the effects of the Coriolis force due to the rotation of fluids and finite electric conductivity. In other investigations, many authors have considered the MHD instabilities in anisotropic plasmas with the influences of the Hall current and finite electric and thermal conductivities [16][17][18][19][20][21][22].…”