Neutron depolarization studies of Pd-Ni-Fe-P alloy

Bulk metallic glasses based on the quaternary alloy Pd-Ni-Fe-P exhibit interesting phase behavior depending on temperature and applied magnetic field. Previous work has suggested that a range of magnetic phases including paramagnetic, superparamagnetic, ferromagnetic and spin glass can be observed in this system. We have applied one dimensional neutron depolarization to explore the correlation of magnetic moments in Pd40Ni22.5Fe17.5P20 alloy as a function of temperature and applied magnetic field. The results provided evidence for correlation lengths of ~ 200 Å. The nature of the correlations and the formation mechanism of the induced ferromagnetic phase are discusse

Au4V – Moment Stability and Spin Fluctuations in the Ordered Phase

Although neither gold nor vanadium generally possess a magnetic moment, the intermetallic compound Au4V is found to be ferromagnetic below 42K. In this paper we report the results of a muon spin relaxation study of the itinerant electron moment fluctuations in Au4V above the Curie temperature. The temperature dependence of the muon spin relaxation rate is found to be similar to that of the weak itinerant helimagnet, MnSi

Excess Spin and the Dynamics of Antiferromagnetic Ferritin

Temperature-dependent magnetization measurements on a series of synthetic ferritin proteins containing from 100 to 3000 Fe(III) ions are used to determine the uncompensated moment of these antiferromagnetic particles. The results are compared with recent theories of macroscopic quantum coherence which explicitly include the effect of this excess moment. The scaling of the excess moment with protein size is consistent with a simple model of finite size effects and sublattice noncompensation.Comment: 4 pages, 3 Postsript figures, 1 table. Submitted to PR

Preliminary studies of sulphate solubility and redox in 60P2O5–40Fe2O3 glasses

Preliminary studies of sulphate solubility, redox, composition, refractory corrosion and density of 60P2O5–40Fe2O3 (molar percent) glasses are presented. Techniques included Mössbauer spectroscopy and energy-dispersive X-ray spectroscopy. Sulphate solubility of the glass was very low, only 0.01 wt.% SO3. Iron (II) sulphate batch addition resulted in a more reduced glass than a sulphate-free batch. Redox, considered independently of temperature, had no effect on refractory corrosion or melt volatilisation in the range studied. No differences were detected in refractory corrosion using alumina or mullite crucibles. Higher oxygen partial pressure had no effect on iron valence. Values, trends and conclusions relating to density, molar volume, iron environment and iron coordination in these glasses were consistent with the accepted view

A Mössbauer spectroscopy and neutron diffraction study of magnetostrictive, melt-spun Fe-Ga alloy ribbons

Ribbons of Fe100−xGax (x=15, 17.5, 19.5 and 22.5) were prepared by rapid solidification from the melt. 57Fe Mössbauer spectroscopy and high resolution neutron diffraction have revealed that Fe1−xGax alloys with x=15 and 17.5 have the disordered bcc (A2) structure even after annealing, but the alloy with x=19.5 developed the short-range ordered D03 phase when annealed. The x=22.5 alloys showed mainly D03 phase with a fraction of bcc phase. A fraction of the bcc phase transformed into D03 phase and the long-range ordering of D03 phase was improved after annealing. 57Fe Mössbauer spectra showed no observable L12 phase in any samples even though less than 1% volume of L12 phases has been found in the annealed samples by neutron diffraction. The additional absorption at hyperfine field of 25 T in x=22.5 samples was regarded as a result of imperfect D03 structure, rather than L12 phase

Structure and properties of iron borophosphate glasses

Thermal stability, structure and aqueous chemical durability of glasses of nominal composition 60P2O5-40Fe2O3 (mol%) doped with up to 20% B2O3 have been investigated. B2O3 was substituted for either P2O5 or Fe2O3, or was added on a pro rata basis. No substantial melt volatilisation was detected, and refractory corrosion was minimal. Iron cations of both redox states occupied distorted octahedral sites; B2O3 additions did not affect iron coordination, although Tg and the Fe2+/ΣFe redox ratio increased. Addition of up to 10% B2O3 did not significantly affect durability but it improved thermal stability and increased liquidus temperature. Chemical durability (as measured by the product consistency test, PCT) decreased by approximately one order of magnitude for every further 5% B2O3 addition above 10% when substituted for Fe2O3. Thermal analysis indicated increasing glass stability with increasing B2O3 content. X-ray diffraction showed that one sample of nominal composition 50P2O5-40Fe2O3-10B2O3 developed crystalline B0·57Fe0·43PO4 or a similar phase during cooling. There was no evidence that this significantly affected chemical durability. The addition of B2O3 at low levels (<10%) may be useful in improving the performance of iron phosphate glasses for applications such as waste immobilisation or sealing glasses