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The crystal structures and magnetic properties of three compounds within the system BaIrxFe1-xO3-δ have been investigated using a combination of X-ray and neutron powder diffraction, high resolution transmission electron microscopy and d.c. SQUID magnetometry. BaIr0.2Fe0.8O2.932(5) and BaIr 0.6Fe0.4O3 adopt the 6H structure (space group P63/mmc, a = 5.72 Å, c = 14.15 Å), whilst BaIr 0.3Fe0.7O2.949(7) exists in the rare 15R modification (space group R3̄m, a ≈ 5.73 Å, c ≈ 35.55 Å). Both structures comprise dimers of face-sharing octahedra as well as octahedra which share only vertices with their neighbours. For 6H BaIr0.2Fe0.8O2.932(5) and 15R BaIr0.3Fe 0.7O2.949(7) neutron diffraction experiments show an antiferromagnetically ordered state at 2 K. TN has been identified through variable temperature neutron diffraction to be 200(4) K for 15R BaIr0.3Fe0.7O2.949(7). In both of these samples a proportion of the spins remain decoupled from the magnetic backbone and there is evidence for a spin-glass freezing transition at low temperatures. Susceptibility data for 6H BaIr0.6Fe0.4O3 indicate a single transition to a spin-glass state.

This study concerns the bulk mica phase of a barium phlogopite glass–ceramic, with potential applications in Computer Aided Design and Computer Aided Manufacturing in dentistry, which has been studied in detail and characterized for the first time. A number of analytical techniques including powder X-ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy, electron micro-probe analysis (EMPA), single crystal XRD and Monte-Carlo methods have been used to determine the mica phase composition and crystallographic structure. This has led to the identification of a new species of trioctahedral interlayer deficient brittle mica with an ideal formula of Ba2/3Mg3(Si8/3Al4/3)O10F2. Monte-Carlo simulations of Si/Al cation ordering indicate that the (Si8/3Al4/3) tetrahedral composition is unique and energetically favoured over that of the original assumed mica phase of Ba0.5Mg3(Si3AlO10)F2. The general mica composition X0.5Mg3(Si3Al)O10F2 where X is a divalent interlayer cation; therefore, does not precipitate in brittle mica glass–ceramics.

Electron-transfer processes play a vital role in many biological phenomena, from energy storage to photosynthesis. Positive muons allow such transfer processes in macromolecules, such as proteins, to be probed on a microscopic level. We have used this probe via muon spin relaxation (μSR) to investigate electron-transfer processes in ferritin; the normal iron storage protein. Data collected at finite fields is well described using the Risch-Kehr model at all measured temperatures with inter and intra-chain diffusion rates of 109 and 1011 rad s-1 being determined respectively. The results are compared to similar measurements on other proteins.

The biomineralization of human dental enamel has resulted in a highly anisotropic and heterogeneous distribution of hydroxyapatite crystallites, which in combination with its high mineral content has resulted in one of the most durable and hardest tissues in the human body. In this study, we used position-sensitive synchrotron X-ray diffrac- tion to quantify the spatial variation in the direction and magnitude of the preferred orientation of enamel crystallites across a whole tooth crown. Two-dimensional syn-chrotron X-ray diffraction images were collected with 300 lm spatial resolution over a series of six sequential tooth sections obtained from a single maxillary first premolar and were analyzed using Rietveld refinement. Both the magnitude and the direction of the crystallite orientation were found to have a high spatial heterogeneity. Areas of high crystallite alignment were directed perpendicular to the biting surfaces, which is thought to meet the functional requirements of mastication. The results may assist in our understanding of the structure–function relationship and of the evolutionary development of enamel.

Modified iron phosphate glasses have been prepared with nominal molar compositions [(1�x)�(0.6P2O5–\ud 0.4Fe2O3)]�xRySO4, where x = 0–0.5 in increments of 0.1 and R = Li, Na, K, Mg, Ca, Ba, or Pb and y = 1 or 2. In\ud most cases the vast majority or all of the sulfate volatalizes and quarternary P2O5–Fe2O3–FeO–RyOz\ud glasses or partially crystalline materials are formed. Here we have characterized the structure, thermal\ud properties, chemical durability and redox state of these materials. Raman spectroscopy indicates that\ud increasing modifier oxide additions result in depolymerization of the phosphate network such that the\ud average value of i, the number of bridging oxygens per –(PO4)– tetrahedron, and expressed as Qi,\ud decreases. Differences have been observed between the structural effects of different modifier types\ud but these are secondary to the amount of modifier added. Alkali additions have little effect on density;\ud slightly increasing Tg and Td; increasing a and Tliq; and promoting bulk crystallization at temperatures\ud of 600–700 �C. Additions of divalent cations increase density, a, Tg, Td, Tliq and promote bulk crystallization\ud at temperatures of 700–800 �C. Overall the addition of divalent cations has a less deleterious effect\ud on glass stability than alkali additions. 57Fe Mössbauer spectroscopy confirms that iron is present as Fe2+\ud and Fe3+ ions which primarily occupy distorted octahedral sites. This is consistent with accepted structural\ud models for iron phosphate glasses. The iron redox ratio, Fe2+/RFe, has a value of 0.13–0.29 for the\ud glasses studied. The base glass exhibits a very low aqueous leach rate when measured by Product Consistency\ud Test B, a standard durability test for nuclear waste glasses. The addition of high quantities of\ud alkali oxide (30–40 mol% R2O) to the base glass increases leach rates, but only to levels comparable with\ud those measured for a commercial soda-lime-silica glass and for a surrogate nuclear waste-loaded borosilicate\ud glass. Divalent cation additions decrease aqueous leach rates and large additions (30–50 mol%\ud RO) provide exceptionally low leach rates that are 2–3 orders of magnitude lower than have been measured\ud for the surrogate waste-loaded borosilicate glass. The P2O5–Fe2O3–FeO–BaO glasses reported here\ud show particular promise as they are ultra-durable, thermally stable, low-melting glasses with a large\ud glass-forming compositional range.

Quasi-elastic neutron scattering (QENS) has been used to study the deviation from Debye-law harmonic behavior in lyophilized and hydrated apoferritin, a naturally occurring, multisubunit protein. Whereas analysis of the measured mean squared displacement (msd) parameter reveals a hydration-dependent inflection above 240 K, characteristic of diffusive motion, a hydration-independent inflection is observed at 100 K. The mechanism responsible for this low-temperature anharmonic response is further investigated, via analysis of the elastic incoherent neutron scattering intensity, by applying models developed to describe side-group motion in glassy polymers. Our results suggest that the deviation from harmonic behavior is due to the onset of methyl group rotations which exhibit a broad distribution of activated processes ( E a,ave = 12.2 kJ.mol (-1), sigma = 5.0 kJ x mol (-1)). Our results are likened to those reported for other proteins.

We have used synchrotron x-ray diffraction to study the crystal orientation in human dental enamel as a function of position within intact tooth sections. Keeping tooth sections intact has allowed us to construct 2D and 3D spatial distribution maps of the magnitude and orientation of texture in dental enamel. We have found that the enamel crystallites are most highly aligned at the expected occlusal points for a maxillary first premolar, and that the texture direction varies spatially in a three dimensional curling arrangement. Our results provide a model for texture in enamel which can aid researchers in developing dental composite materials for fillings and crowns with optimal characteristics for longevity, and will guide clinicians to the best method for drilling into enamel, in order to minimize weakening of remaining tooth structure, during dental restoration procedures.

Bioactive fluormica–fluorapatite glass-ceramic materials offer a very encouraging solution to the problem of efficient restoration and reconstruction of hard tissues. To produce material with the desired crystalline phases, a five-stage heat treatment must be performed. This thermal processing has a large impact on the microstructure and ultimately the final mechanical properties of the materials. We have examined the thermal processing of one of our most promising machinable biomaterials, using time-resolved small angle neutron scattering and neutron diffraction to study the nucleation and growth of crystallites. The processing route had already been optimized by studying the properties of quenched samples using x-ray diffraction, mechanical measurements and differential thermal analysis. However these results show that the heat treatment can be further optimized in terms of crystal nucleation, and we show that these techniques are the only methods by which a truly optimized thermal processing route may be obtained.

Preliminary studies of sulphate solubility, redox, composition, refractory corrosion and density of 60P2O5–40Fe2O3 (molar percent) glasses are presented. Techniques included Mossbauer 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.

Electron-transfer processes play a vital role in many biological phenomena, from energy storage to photosynthesis. The labelled electron method using positive muons allows such transfer processes in macromolecules, such as proteins, to be probed on a microscopic level. Here we present the results of an experiment using the labelled electron method with mSR to investigate electron-transfer processes in apoferritin. The data is well described using the Risch–Kehr model and the results suggest one dimensional, or intra-chain diffusion occurs in this system. Intra-chain diffusion rates of 1012 rad/s have been determined.

The kinetics of Nb3Sn phase formation in commercial multifilamentary wires have been studied as a function of time and temperature using time-resolved, in situ neutron diffraction. This work shows that at higher temperatures the Nb3Sn phase forms in a fraction of the recommended annealing time. A temperature-independent Avrami exponent of n = 0.51 ± 0.01 was observed, indicating a diffusion-controlled growth mechanism, and a large apparent activation energy of Ea = 10 ± 1 eV is reported where the energies of nucleation and growth both contribute.

Zero-field 57Fe Mossbauer spectroscopy has been used to study the magnetic properties of an amorphous melt-spun Pd40Ni40−x FexP20 (x=5, 10, 17.5, 20) series. The alloys show quadrupole split doublets at room temperature indicating paramagnetic behaviour. At low temperatures the Mossbauer spectra are sextets due to the onset of long range order. The transition temperatures increase with Fe concentration from 12±2 K for Pd40Ni35Fe5P20 to 42.0±2.0 K for Pd40Ni20Fe20P20. The hyperfine field was found to follow Hf(0)(1−T/Tc)β over the critical region with the β exponent being close to 0.4.

The development of high intensity neutron sources coupled with improvements in instrumentation has made it possible to collect high quality diffraction patterns extremely rapidly, and studies of the kinetics of solid-state processes in real time are now feasible. As a consequence, it is now possible to monitor and optimise production processes in the neutron beam using kinetic neutron diffraction. To illustrate the power of the technique three studies of processing routes are described, one in magnet technology and two in biomaterials science.

We have used kinetic neutron diffraction to study phase formation and transformations occurring in Nb–Sn–Cu cables during the fabrication of Nb3Sn wires, a process which currently takes ∼300 h. Our results have shown that complete homogenization of Cu and Sn does not occur during the initial processing stages, and that Nb3Sn is formed in a fraction of the recommended annealing time. This raises the question of the need for the extended processing route when it does not appear to produce significant changes in the structural properties of the wire.

This paper presents the results of muon spin relaxation measurements on a powdered sample of NaV 6 O 11 . Below the ferromagnetic transition temperature, T C =64 K, rapidly damped oscillatory spectra are observed, which can be modelled by the sum of two cosine functions with different frequencies. The low frequency component is associated with muons in or near V 3 O 11 layers. The two-dimensional (2d) character of the ferromagnetic order within this layer gives rise to 2d Ising-like critical scaling of the temperature dependence of the field. The high frequency component is associated with a muon site close to V 3 O 8 layers. The field associated with this component shows a 3d Ising-like temperature dependence above 40 K. There is a marked deviation of the temperature dependence of the high frequency component from the 3d Ising model below 40 K. This coincides with the temperature of the hexagonal to orthorhombic structural phase transition and is the first evidence of any magnetic anomaly being associated with this structural phase transition

The magnetic ground state of a well-characterised and highly ordered Ni3Al sample has been studied by muon spin relaxation. Although it is widely accepted that Ni3Al is an archetypal homogeneous weak itinerant electron ferromagnet with a Curie temperature of 40 K, our μSR measurements provide no evidence of long-range magnetic order, but instead indicate the evolution of an inhomogeneous magnetic ground state at temperatures below 40 K in which relatively static magnetic clusters coexist with a spin fluctuating state.

We present further experimental and theoretical insights into unusual ‘two-component’ antiferromagnetic critical phenomena in uranium antimonide. High resolution neutron powder diffraction measurements have been used to quantitatively describe the growth of the staggered magnetisation below T N ∼212 K. Further insight into the critical properties of USb has been provided by vibrating sample magnetometry. The observed susceptibility is found to increase on warming towards T N in a manner compatible with 3D Heisenberg behaviour. The data are discussed in the context of previous observations of two-component X-ray critical scattering (Phys. Rev. B 54 (1996) 15234). Scaling and related considerations are applied to the critical exponents determined by the different techniques. The scaling properties provide insights into the possible origin of unusual ‘two-component’ critical phenomena in this material.

D3OFe3(SO4)2(OD)6 is a model example of an S = 5/2 Kagome anti-ferromagnet that exhibits unconventional two-dimensional spin-glass properties. We report quasi-elastic neutron-scattering data on D3OFe3(SO4)2(OD)6 derived from three-directional neutron spin-polarization analysis in combination with time-of-flight analysis (Δ E [Formula: see text] 1 meV). At 1.5 K, within the time window of the experiment, only 45% of the total elastic magnetic moment is frozen — a broad magnetic response in Q is still observed at temperatures in excess of ten times the spin-glass freezing temperature. The dc-magnetization measurements on H3OFe3–xAlx(SO4)2(OD)6 show that dilution of the magnetic lattice with Al3+ disrupts the spin-glass state. Mössbauer measurements indicate that the Al replaces the Fe ions on the magnetic sites of the Kagome lattice, giving rise to two distinct iron sites with equal occupation levels but different hyperfine fields. PACS Nos.: 75.10N, 75.30C, 75.30H, 75.50L

Mossbauer spectroscopy has been used to study iron uptake and translocation in rice plants. Spectra were collected from intact root and leaf tissue of rice plants grown in anaerobic 57Fe(II)-enriched nutrient solutions. The spectra obtained from root tissue of plants grown in nutrient solutions typical of paddy soils arise primarily from Fe(III)-oxide components precipitated on the root cell walls. In contrast, the spectra obtained from root tissue from plants exposed to lower, toxic, pH conditions show that, in addition to Fe(III), uncomplexed Fe(II) is taken up. No evidence of Fe(II) was seen in the leaf tissue of any of the plants, where the spectra are characteristic of Fe(III) in ferritin and other complexed forms.

Neutron polarisation studies of the diffuse scattering from disordered magnetic alloys and compounds have provided unique and detailed insights into the nature and extent of magnetic inhomogeneities and their dependence upon local atomic environments. In this paper, we briefly review the application of polarised neutron methods in the characterisation of magnetic and structural defects in ferromagnets, antiferromagnets, spin glasses and topologically frustrated systems and present some new polarisation analysis measurements of the spin correlations in β-MnAl.

Soils from North East Libya have been investigated by X‐ray diffraction, chemical analysis and Mossbauer spectroscopy. Quartz, kaolinite and illite were the main components identified by XRD in all specimens. Total and poorly ordered iron oxides were estimated using dithionite–citrate–bicarbonate (DCB) and oxalate extraction methods, respectively; in all cases, the oxalate‐extractable iron represents a relatively minor fraction. Mossbauer spectroscopy showed the presence of substantial quantities of haematite and goethite, both in microcrystalline forms, but there was no systematic relationship between the relative proportions of these phases and the geographical origins of the soils.

Using the technique of muon spin relaxation (µSR), repolarisation curves are determined following the deposition of positive muons in samples of apoferritin over the temperature range 50 K to 270 K, and ferritin over the temperature range 15 K to 280 K. Evidence is found for a muonium-substituted species common to both apoferritin and ferritin. In apoferritin at 270 K an estimate for A′, the reduced isotropic muon–electron hyperfine coupling constant, is 168±39 MHz. In ferritin at 280 K the value for A′ is 164±37 MHz.

We are currently developing machinable and load-bearing mica-based glass-ceramics for use in restorative dental surgery. In this paper we present the results of an ambient temperature small angle neutron scattering (SANS) study of several such ceramics with chemical compositions chosen to optimise machinability and strength. The SANS spectra are all dominated by scattering from the crystalline–amorphous phase interface and exhibit Q−4 dependence (Porod scattering) indicating that, on a 100 A scale, the surface of the crystals is smooth.

This paper presents the results of a temperature-dependent 57 Fe Mossbauer spectroscopy study of a new Y–Fe phase. Three magnetically ordered and three non-magnetic Fe sites are present in the material below 56 K. Below 50 K the temperature dependence of the hyperfine fields is dominated by spin wave excitations. As the ordering temperature is approached there is a sudden collapse of the hyperfine field.

Ribbons of Fe100−xGax (x=15, 17.5, 19.5 and 22.5) were prepared by rapid solidification from the melt. 57Fe Mossbauer spectroscopy and high resolution neutron diffraction have revealed that Fe100−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 Mossbauer 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.

The fabrication of highly-oriented polycrystalline ceramics of Bi 5Fe 0.5Co 0.5Ti 3O 15, prepared via molten salt synthesis and uniaxial pressing of high aspect ratio platelets is reported. Electron backscatter images show a secondary phase within the ceramic which is rich in cobalt and iron. The concentration of the secondary phase obtained from scanning electron microscopy is estimated at less than 2% by volume, below the detection limit of x-ray diffraction (XRD). The samples were characterized by x-ray diffraction, polarization-electric field measurements, superconducting quantum interference device as a function of sample orientation and vibrating sample magnetometry as a function of temperature. It is inferred from the data that the observed ferromagnetic response is dominated by the secondary phase. This work highlights the importance of rigorous materials characterisation in the study of multiferroics as small amounts of secondary phase, below the limit of XRD, can lead to false conclusions.

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.

The biomineralization of human dental enamel has resulted in a highly anisotropic and heterogeneous distribution of hydroxyapatite crystallites, which in combination with its high mineral content has resulted in one of the most durable and hardest tissues in the human body. In this study, we used position-sensitive synchrotron X-ray diffraction to quantify the spatial variation in the direction and magnitude of the preferred orientation of enamel crystallites across a whole tooth crown. Two-dimensional synchrotron X-ray diffraction images were collected with 300 μm spatial resolution over a series of six sequential tooth sections obtained from a single maxillary first premolar and were analyzed using Rietveld refinement. Both the magnitude and the direction of the crystallite orientation were found to have a high spatial heterogeneity. Areas of high crystallite alignment were directed perpendicular to the biting surfaces, which is thought to meet the functional requirements of mastication. The results may assist in our understanding of the structure-function relationship and of the evolutionary development of enamel.

The onset of ferromagnetism in Pd1-cNic alloys occurs at c=2.45 %. Dilute Pd-Ni alloys, with c=3.3% and 5.8% (Tc=20.5K and 90K) have been studied withμSR. For transverse field geometry the data show a rapid increase in the relaxation rate as Tc is approached. However when the same alloys were studied in zero field, with longitudinal geometry, there was no sign of significant depolarisation at any temperature down to 12K. This result is attributed to the high mobility of muons in these alloys, resulting in extreme motional narrowing, as the muons sample magnetic domains of many different orientations.

Zero field μSR spectra from Cr85Mo15 are well described by the sum of a lightly damped (0.02μs−1

μSR, high resolution neutron powder diffraction and heat capacity have been used to study the spin fluctuation compound UMn2. The μSR spectra are dominated by muon depolarisation due to static fields from the Mn nuclei, features in the temperature dependence of the associated relaxation rate, σ, correlating well with the structural transitions observed at 210K. While a weak exponential relaxation (λ ∼ 0.01μs−1) indicates the presence of atomic spin fluctuations between 50K and 325K, μSR provides little evidence of moment localisation or long range magnetic order, although an anomalous increase in σ below 40K is observed.

Zero and longitudinal field μSR has been used to probe the magnetic state of amorphous Bi2Sr2CaCu2Ox prepared by rapid quenching from the melt. The results suggest quasi-static spin correlations between extremely dilute Cu2+ ions.

Neutron-diffraction and neutron-polarisation analysis have been used to map the magnetic phase diagram of YBa2(Cu1-xFex)3O6+y, with x=0.06 and 0.10, as a function of oxygen stoichiometry, y. For x=0.06 (y=0.35) and x=0.10 (y

Muon spin rotation (μSR) and magnetisation measurements have been used to characterise the superconducting state of YNi 2 B 2 C below T c = 15 K . A measured B c2 (0) of 6.0(5) T and B c1 (0) of 36.9(5) mT from magnetisation measurements, together with the μSR measurements, provide a coherence length, ξ(0), of 8.1 nm and a magnetic penetration depth, λ(0), of 103 nm. The temperature dependence of the penetration depth deduced from the μSR measurements is consistent with the BCS model and implies conventional s wave pairing in YNi 2 B 2 C. Using these results together with existing thermodynamic data we estimate a superconducting carrier density of 1.9 per formula unit and an electron-mass enhancement factor of 9.4.

The magnetic and structural phase diagrams of the C15 Laves phase system ${\mathrm{Dy}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Y}}_{\mathit{x}}$${\mathrm{Mn}}_{2}$ (0x1) have been mapped in detail using neutron powder diffraction. At concentrations x0.35 and temperatures less than 45 K a complex antiferromagnetic structure, related to that of ${\mathrm{DyMn}}_{2}$, is observed. In this structure only one in four of the chemically equivalent Mn atoms carries a magnetic moment, of magnitude 1.4${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$. This moment is induced by a strong molecular field at this Mn site, which results from the canted magnetic structure of the Dy sublattice. At concentrations greater than x=0.75 the magnetic order is similar to that of ${\mathrm{YMn}}_{2}$: the transition to antiferromagnetism at T100 K is of first order and is accompanied by a 5% expansion of the volume of the unit cell. This is a consequence of the condensation of local Mn moments, of magnitude 2.8${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$, from the spin-fluctuating state which characterizes the paramagnetic phase. For a wide range of intermediate compositions, 0.35x0.75, all long-range magnetic order is lost. However, a small (1%) cell-volume expansion persists across this magnetically disordered phase, implying the presence of an intrinsic Mn moment in this region. It is suggested that the loss of long-range magnetic order at intermediate compositions is due not simply to Dy-Y disorder, but also to competition between the magnetic structures associated with the induced and intrinsic moments.

Neutron powder diffraction has been used to determine the effects of dilute (≤2.5%) Fe substitution on the helical antiferromagnetic order and associated discontinuous magnetic and structural transitions at the Neel point of the frustrated spin fluctuating itinerant electron magnet YMn2.

Oxide materials which exhibit both ferroelectricity and ferromagnetism are of great interest for sensors and memory applications. Layered bismuth titanates with an Aurivillius structure, (BiFeO 3 )nBi 4 Ti 3 O 12 , can possess ferroelectric and ferromagnetic order parameters simultaneously. It has recently been demonstrated that one such example, Bi 5 Fe 0.5 Co 0.5 Ti 3 O 15 , where n = 1 with half the Fe3+ sites substituted by Co3+ ions, exhibits both ferroelectric and ferromagnetic properties at room temperature. Here we report the fabrication of highly-oriented polycrystalline ceramics of this material, prepared via molten salt synthesis and uniaxial pressing of high aspect ratio platelets. Electron backscatter images showed that there is a secondary phase within the ceramic matrix which is rich in cobalt and iron, hence this secondary phase could contribute in the main phase ferromagnetic property. The concentration of the secondary phase obtained from secondary electron microscopy is estimated at less than 2.5 %, below the detection limit of XRD. TEM was used to identify the crystallographic structure of the secondary phase, which was shown to be cobalt ferrite, CoFe 2 O 4 . It is inferred from the data that the resultant ferromagnetic response identified using VSM measurements was due to the presence of the minor secondary phase. The Remanent magnetization at room temperature was M r ≈ 76 memu/g which dropped down to almost zero (M r ≈ 0.8 memu/g) at 460 °C, far lower than the anticipated for CoFe 2 O 4 .

We present an overview of two leading methods of determining probability distributions from Mossbauer spectra, using the model amorphous magnet Fe(80)B(20). A comparison is made between the maximum-entropy method, which permits analysis using truly arbitrary parameter probability distributions, and a Voigtian-based analysis, which uses a sum of Gaussian components to create parameter distributions of pseudo-arbitrary shape. Our results indicate that, in Fe(80)B(20), a Gaussian distribution of magnetic hyperfine fields is a very good approximation, although small deviations from a Gaussian shape are evident. We find that the apparent existence of correlations between the isomer shift and magnetic hyperfine field parameters, as found using Voigt-based analyses, may be an artefact of imposing a Gaussian shape on the parameter distributions. We conclude that maximum entropy and Voigtian analyses together provide a very powerful means of characterizing magnetic materials with Mossbauer spectroscopy.

Laser-Induced Breakdown Spectroscopy (LIBS) was applied to the analysis of bioceramic\ud samples. The relationship between sample hardness and LIBS plasma\ud properties was investigated, with comparison to conventional Vickers hardness\ud measurements. The plasma excitation temperature Te was determined using the lineto-\ud continuum ratio for the Si (I) 288.16 nm emission line; we have demonstrated a\ud linear relationship between sample surface hardness and plasma temperature. Results\ud indicate that hardness determination based on measurements of Te offers greater\ud reproducibility than Vickers hardness measurements, under the conditions considered\ud here. The validity of spectroscopic diagnostics based on LTE was confirmed.

The neutron polarisation analysis technique has been used to investigate the possibility of antiferromagnetic order in α-Ti. The results show no evidence of such order, and moreover, place an upper limit of 0.01μB Ti atom on any paramagnetic contribution to the scattering. While the measured isotopic incoherent cross-section of Ti, σII = 2.19 ± 0.02 b/atom, is in reasonable agreement with the previously reported value, the spin incoherent cross-section, σSI is measured to be 0.091 ± 0.006 b/atom, significantly lower than the accepted value of 0.29 b/atom.

The crystal and magnetic structure of the C15 Laves phase of HoMn2 was restudied using powder neutron diffraction. High-resolution spectra showed HoMn2 to remain cubic Fd3m below the magnetic transition temperature. The Ho spins assume a spin-canted ferromagnetic structure with 7.9 mu B per Ho atom. One out of four Mn sites carries a moment of 0.6 mu B induced by the strongly polarizing magnetic environment of ferromagnetically coupled near-neighbour (111) planes of rare-earth spins. A small thermal expansion anomaly accompanied by a spin reorientation is found at the Curie point of 25 K; the Neel point of the system lies at 31 K.

We have applied x-ray magnetic circular dichroism to investigate the field-induced ferromagnetism\ud in Pd40Ni22.5Fe17.5P20 alloy. The experiment revealed that both Ni and Fe were in a divalent state and\ud that the magnetic properties of the material were determined by the localized 3d electrons of the\ud transition metals. No clear evidence of Ruderman–Kittel–Kasuya–Yosida-type interaction among\ud magnetic clusters was observed. It is believed that the detailed balance of fundamental spin-orbit\ud and exchange interactions as a function of temperature and applied magnetic field determine the\ud different magnetic properties of the alloy.

High-resolution neutron powder diffraction and transverse field mu SR measurements have been used to examine the nature of the magnetic and structural transition at 100 K in YMn2. The neutron measurements indicate a first-order hysteretic transition occurring at 92.5 K on cooling and 108 K on warming. The low-temperature phase is tetragonal (c/a=0.995) and antiferromagnetic with localized Mn moments of 2.8 mu B ordering in a long-wavelength helix characterized by an antiferromagnetic translation vector ( tau , tau ',1) where tau =0.018 and tau '=0.003. The high-temperature phase is cubic and Pauli paramagnetic. The collapse of the Mn moment at the transition is accompanied by a 5% decrease in the cell volume. In the paramagnetic state of YMn2 measurement of the muon transverse relaxation rate reveals an underlying second-order transition which the authors associate with the critical slowing of longitudinal spin fluctuations as the transition temperature is approached.

Neutron polarisation analysis measurements reveal antiferromagnetic spin correlations persisting to temperatures of 120 K in Pauli paramagnetic Y(Mn1−xFe x )2, 0.03≤x≤0.05. The mean moment at the Mn(Fe) site is found to be 0.2μB. Transverse field μSR is characterised by weak exponential damping with a rate of 0.02 μs−1 at 300 K increasing according to the power lawT−0.75 to only 0.16μ S −1 at 12 K. It is suggested that these results are consistent with a slowing down of longitudinal spin fluctuations at the Mn site as temperature decreases.

Melt-spun Fe–Ga ribbons were prepared and some ribbons were annealed at 1000 °C for 1 h then\ud slowly cooled to room temperature. X-ray diffraction patterns revealed no evidence of texture and\ud only bcc phase in the as-quenched ribbons. However, high-resolution neutron diffraction patterns\ud gave more information on the structure of these ribbons. Only diffractions from the disordered bcc\ud A2 phase were found in as-quenched ribbons with 15, 17.5, and 19.5 at. % Ga content, without any\ud trace of satellite peaks or splitting peaks from the proposed Ga–Ga pairing superlattice structure.\ud The broadening of the base of the �110� peaks for all samples except the as-quenched 15 at. % Ga\ud ribbon might indicate the existence of some kind of short range ordering. Ribbons developed L12\ud phase after annealing especially in the Fe 19.5 at. % Ga ribbon where the formation of L12 phase\ud reduced the Ga content in the remaining A2 phase and decreased its lattice parameter dramatically.\ud D03 phase formed in the as-quenched 22.5 at. % Ga ribbon and the following annealing treatment\ud transformed more A2 phase into D03 phase.

We have used synchrotron X-ray diffraction to study the texture and the change in lattice parameter as a function of position in a cross section of human dental enamel. Our study is the first to map changes in preferred orientation and lattice parameter as a function of position within enamel across a whole tooth section with such high resolution. Synchrotron X-ray diffraction with a micro-focused beam spot was used to collect two-dimensional (2D) diffraction images at 150 microm spatial resolution over the entire tooth crown. Contour maps of the texture and lattice parameter distribution of the hydroxyapatite phase were produced from Rietveld refinement of diffraction patterns generated by azimuthally sectioning and integrating the 2D images. The 002 Debye ring showed the largest variation in intensity. This variation is indicative of preferred orientation. Areas of high crystallite alignment on the tooth cusps match the expected biting surfaces. Additionally we found a large variation in lattice parameter when travelling from the enamel surface to the enamel-dentine junction. We believe this to be due to a change in the chemical composition within the tooth. The results provide a new insight on the texture and lattice parameter profiles within enamel.