Decrease In Iron Content Research Articles

Placental cadmium and progesterone concentrations in cigarette smokers

Cadmium and progesterone concentrations were evaluated in term placentas collected from 56 healthy parturients in the city of Zagreb. Concentrations of lead, iron, zinc, and copper in placentas were analyzed. Data collected by questionnaire identified 29 nonsmoking and 27 smoking women. From each placenta, three samples from different locations were taken. Metals were measured by atomic absorption spectrometry. Progesterone was determined by specific radioimmunoassay in homogenized and lyophilized tissue samples after steroid extraction with ethanol. No effect of sample location was found. In placentas of smoking women an increase in cadmium, reduced progesterone and a decrease in iron concentrations were found. Placental copper and zinc concentrations were not altered. In conclusion, the results present new evidence that maternal smoking reduces placental progesterone content and support the established association of smoking with placental cadmium.

Appearance of ferromagnetism in f.c.c. solid solutions of binary and ternary Fe–Cu-based systems prepared by mechanical alloying technique

The ferromagnetic f.c.c. solid solutions are formed by mechanical alloying in the Fe–Cu binary systems containing less than 60% of iron. The Curie temperature of the alloy decreases with decreasing iron concentration. The expansion of average atomic volume of the alloys is about 1.6% of pure copper and 5.3% of f.c.c. γ-iron regardless of copper content except for dilute iron alloys. It is suggested from the present work that the ferromagnetism in the Fe–Cu alloys originates when the atomic volume is expanded by a certain value (5.3% of γ-iron is enough), and when a certain number of neighboring iron atoms exist to percolate the ferromagnetic interaction and possibly to generate the magnetic moment of iron. In the studies of ternary systems silver atoms hardly dissolved in Fe–Cu solution, whereas gold atoms formed solid solution.

Increased nitric oxide is one of the causes of changes of iron metabolism in strenuously exercised rats.

This study was carried out to investigate the possible role of increased nitric oxide (NO) production in the development of the low iron status in strenuously exercised rats. Female Sprague-Dawley rats were randomly assigned to four groups: sedentary (S1), sedentary + nitro-L-arginine methyl ester (L-NAME; S2), exercise (E1), and exercise + L-NAME (E2). Animals in the E1 and E2 groups swam for 2 h/day for 3 mo. L-NAME in the drinking water (1 mg/ml) was administrated to rats in the S2 and E2 groups for the same period. At the end of third month, hematological indexes and nitrite and nitrate (NOx) contents in the plasma and non-heme iron and NOx levels in the liver, spleen, and bone marrow cells were measured. Three months of exercise induced a significant increase in NOx content and a decrease in iron level both in plasma and tissues. Treatment with L-NAME, an inhibitor of NO synthase (NOS), led to a significant decrease in NOx and an increase in iron level both in plasma and tissues in the exercised rats. The E2 group had a significantly lower NOx content as well as a higher iron level both in plasma and tissues than the E1 group. However, the iron contents in the plasma and tissues of the E2 group were still significantly lower than those found in S1. No difference was found in NOx levels between E2 and S1. These findings showed that exercise was associated with elevation in NOx and reduction in iron in plasma and the tissues. Treatment with L-NAME was able to completely inhibit the effect of exercise on NOx as well as partly recover the decreased iron contents in plasma and tissues resulting from exercise. This suggests that the increased production of NO might be one of the causes of the lower iron status in exercised rats.

Conductivity and dielectric behaviour of iron sodium phosphate glasses

Abstract Glasses of the composition (Na 2 P 2 O 6 ) 100− x (Fe 2 O 3 ) x , with x =5, 10, 20 and 25 mol%, have been prepared. The alternating current conductivity, the dielectric permittivity and the loss were measured in the frequency range 0.12–10 2 kHz and in the temperature range 323–623 K. The results show that the contribution of the electronic conduction to the conductivity decreases with decreasing iron concentration. The electronic conduction is possibly due to hopping of an electron from the lower valance state of Fe 2+ to the higher valance state of Fe 3+ ions. The results of the dielectric permittivity show that no maximum was observed in the temperature and frequency range studied. This absence is an indication of non-ferroelectric behaviour of all the samples. However, the thermal activated relaxation mechanism dominates the observed relaxation behaviour. The distribution of the relaxation processes was also studied, and three processes were adequate to describe the present results.

The fate of added iron during a mesoscale fertilisation experiment in the Southern Ocean

The first Southern Ocean Iron RElease Experiment (SOIREE) was performed during February 1999 in Antarctic waters south of Australia (61°S, 140°E), in order to verify whether iron supply controls the magnitude of phytoplankton production in this high nutrient low chlorophyll (HNLC) region. This paper describes iron distributions in the upper ocean during our 13-day site occupation, and presents a pelagic iron budget to account for the observed losses of dissolved and total iron from waters of the fertilised patch. Iron concentrations were measured underway during daily transects through the patch and in vertical profiles of the 65-m mixed layer. High internal consistency was noted between data obtained using contrasting sampling and analytical techniques. A pre-infusion survey confirmed the extremely low ambient dissolved (0.1 nM) and total (0.4 nM) iron concentrations. The initial enrichment elevated the dissolved iron concentration to 2.7 nM. Thereafter, dissolved iron was rapidly depleted inside the patch to 0.2-0.3 nM, necessitating three re-infusions. A distinct biological response was observed in iron-fertilised waters, relative to outside the patch, unequivocally confirming that iron limits phytoplankton growth rates and biomass at this site in summer. Our budget describing the fate of the added iron demonstrates that horizontal dispersion of fertilised waters (resulting in a quadrupling of the areal extent of the patch) and abiotic particle scavenging accounted for most of the decreases in iron concentrations inside the patch (31-58 and 12-49 of added iron, respectively). The magnitude of these loss processes altered towards the end of SOIREE, and on days 12-13 dissolved (1.1 nM) and total (2.3 nM) iron concentrations remained elevated compared to surrounding waters. At this time, the biogenic iron pool (0.1 nM) accounted for only 1-2 of the total added iron. Large pennate diatoms (> 20 μm) and autotrophic flagellates (2-20 μm) were the dominant algal groups in the patch, taking up the added iron and representing 13 and 39 of the biogenic iron pool, respectively. Iron regeneration by grazers was tightly coupled to uptake by phytoplankton and bacteria, indicating that biological Fe cycling within the bloom was self-sustaining. A concurrent increase in the concentration of iron-binding ligands on days 11-12 probably retained dissolved iron within the mixed layer. Ocean colour satellite images in late March suggest that the bloom was still actively growing 42 days after the onset of SOIREE, and hence by inference that sufficient iron was maintained in the patch for this period to meet algal requirements. This raises fundamental questions regarding the biogeochemical cycling of iron in the Southern Ocean and, in particular, how bioavailable iron was retained in surface waters and/or within the biota to sustain algal growth. © 2001 Elsevier Science Ltd.

Magnetic poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) microspheres by dispersion polymerization

Crosslinked poly(2-hydroxyethyl methacrylate)-based magnetic microspheres were prepared in a simple one-step procedure by dispersion polymerization in the presence of several kinds of iron oxides. Cellulose acetate butyrate and dibenzoyl peroxide were used as steric stabilizer and polymerization initiator, respectively, and ethylene dimethacrylate was a crosslinking agent. The resulting product was characterized in terms of particle size, particle size distribution, iron(III) content, and magnetic properties. In the presence of needle-like maghemite in the polymerization mixture and under suitable conditions, magnetic microspheres with relatively narrow size distribution were formed. An increase in the particle size and, at the same time, a decrease in molecular weight of uncrosslinked polymers resulted, as the continuous phase became richer in 2-methylpropan-1-ol. Coercive force of needle-like maghemite-containing particles was higher than that of cubic magnetite-loaded microspheres. Coercive force increased with the decreasing iron content in the particles. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1161–1171, 2000

Interaction of Aluminum with Exogenous and Endogenous Iron in the Organism of Rats

The aim of these experiments was to find changes in free erythrocyte protoporphyrins (FEP) and in the concentration of endogenous iron in the blood, erythrocytes, serum, liver, kidneys, and spleen of rats, as well as in the dynamics of aluminum concentrations in the serum of rats after oral application of aluminum chloride (AlCl3) separately or with ferrum chloride (FeCl2), depending on the time and doses administered. The experiments were carried out on female Wistar rats which received (p.o.) 100 mg Al/kg separately or with iron (4 mg Fe/kg) daily for 35 days. The effects of aluminum administration were noticed after the second week. The experiments demonstrated that the increase in the level of free erythrocyte protoporphyrins in the blood is the most sensitive indicator of exposure to AlCl3. A decrease in iron concentration in erythrocytes, blood, and spleen was also noticed. The response and the sequence of the investigated effects were recorded according to aluminum and iron concentration in the serum. Joint administration of iron and aluminum decreases concentration of aluminum in serum and prevents changes in the investigated indicators in rats exposed to aluminum chloride.

Magnetic poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) microspheres by dispersion polymerization

Crosslinked poly(2-hydroxyethyl methacrylate)-based magnetic microspheres were prepared in a simple one-step procedure by dispersion polymerization in the presence of several kinds of iron oxides. Cellulose acetate butyrate and dibenzoyl peroxide were used as steric stabilizer and polymerization initiator, respectively, and ethylene dimethacrylate was a crosslinking agent. The resulting product was characterized in terms of particle size, particle size distribution, iron(III) content, and magnetic properties. In the presence of needle-like maghemite in the polymerization mixture and under suitable conditions, magnetic microspheres with relatively narrow size distribution were formed. An increase in the particle size and, at the same time, a decrease in molecular weight of uncrosslinked polymers resulted, as the continuous phase became richer in 2-methylpropan-1-ol. Coercive force of needle-like maghemite-containing particles was higher than that of cubic magnetite-loaded microspheres. Coercive force increased with the decreasing iron content in the particles. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1161–1171, 2000

Localized Sulfate‐Reducing Zones in a Coastal Plain Aquifer

AbstractHigh concentrations of dissolved iron in ground water of coastal plain or alluvial aquifers contribute to the biofouling of public supply wells for which treatment and remediation is costly. Many of these aquifers, however, contain zones in which microbial sulfate reduction and the associated precipitation of iron‐sulfide minerals decreases iron mobility. The principal water‐ bearing aquifer (Magothy Aquifer of Cretaceous age) hi Suffolk County, New York, contains localized sulfate‐redudng zones hi and near lignite deposits, which generally are associated with clay lenses. Microbial analyses of core samples amended with [14C]‐acetate indicate that microbial sulfate reduction is the predominant terminal‐electron‐accepting process (TEAP) in poorly permeable, lignite‐rich sediments at shallow depths and near the ground water divide. The sulfate‐reducing zones are characterized by abundant lignite and iron‐sulfide minerals, low concentrations of Fe(III) oxyhydroxides, and by proximity to clay lenses that contain pore water with relatively high concentrations of sulfate and dissolved organic carbon. The low permeability of these zones and, hence, the long residence time of ground water within them, permit the preservation and (or) allow the formation of iron‐sulfide minerals, including pyrite and marcasite. Both sulfate‐reducing bacteria (SRB) and iron‐reducing bacteria (IRB) are present beneath and beyond the shallow sulfate‐reducing zones. A unique Fe(HI)‐reducing organism, MD‐612, was found in core sediments from a depth of 187 m near the southern shore of Long Island. The distribution of poorly permeable, lignite‐rich, sulfate‐reducing zones with decreased iron concentration is varied within the principal aquifer and accounts for the observed distribution of dissolved sulfate, iron, and iron suit Ides in the aquifer. Locating such zones for the placement of production wells would be difficult, however, because these zones are of limited aerial extent.

Active and Higher Intracellular Uptake of 5-Aminolevulinic Acid in Tumors may be Inhibited by Glycine

Topical 5-aminolevulinic acid is used for the fluorescence-based diagnosis and photodynamic treatment of superficial precancerous and cancerous lesions of the skin. Thus, we investigated the kinetics of 5-aminolevulinic acid-induced fluorescence and the mechanisms responsible for the selective formation of porphyrins in tumors in vivo. Using amelanotic melanomas (A-Mel-3) grown in dorsal skinfold chambers of Syrian golden hamsters fluorescence kinetics were measured up to 24 h after topical application of 5-aminolevulinic acid (1%, 3%, or 10%) for 1 h, 4 h, or 8 h by intravital microscopy (n = 54). Maximal fluorescence intensity in tumors after 1 h application (3% 5-aminolevulinic acid) occurred 150 min and after 4 h application (3% 5-aminolevulinic acid) directly thereafter. Increasing either concentration of 5-aminolevulinic acid or application time did not yield a higher fluorescence intensity. The selectivity of the fluorescence in tumors decreased with increasing application time. Fluorescence spectra indicated the formation of protoporphyrin IX (3% 5-aminolevulinic acid, 4 h; n = 3). The simultaneous application of 5-aminolevulinic acid (3%, 4 h) and glycine (20 microM or 200 microM; n = 10) reduced fluorescence in tumor and surrounding host tissue significantly. In contrast, neither decreasing iron concentration by desferrioxamine (1% and 3%; n = 10) nor inducing tetrapyrrole accumulation using 1, 10-phenanthroline (7.5 mM; n = 5) increased fluorescence in tumors. The saturation and faster increase of fluorescence in the tumor together with a reduction of fluorescence by the application of glycine suggests an active and higher intracellular uptake of 5-aminolevulinic acid in tumor as compared with the surrounding tissue. Shorter application (1 h) yields a better contrast between tumor and surrounding tissue for fluorescence diagnosis. The additional topical application of modifiers of the heme biosynthesis, desferrioxamine or 1,10-phenanthroline, however, is unlikely to enhance the efficacy of topical 5-aminolevulinic acid-photodynamic therapy at least in our model.

Hyperfine fields and Fe magnetic moments in Fe-Rh alloys; a Mössbauer spectroscopy study

The Mössbauer spectra of the melt-spun and subsequently intensively ball-milled Fe 65Rh 35, Fe 50Rh 50 and Fe 26Rh 74 alloys with fcc structure are characterized at 4.2 K by broad hyperfine field distributions. The magnetic critical temperatures are 60(5) for the first one and, respectively, 85(5) K for the second and the latter composition, in good agreement with recent magnetic susceptibility studies. The distributions arise as result of the chemical disorder, local strains and atomic displacements, owing to the drastic ball-milling process. The values of the Fe magnetic moments at the peaks of the hyperfine field distributions reached 1.1, 1.6 and 1.9 μ B with decreasing iron concentration in semi-quantitative agreement with earlier experimental and recent theoretical evaluations of Fe moments in gamma-Fe and fcc Fe 50Rh 50. Above 400 K an irreversible transformation to the bcc structure occurs for the two Fe-rich alloys with three types of Fe sites in the Fe richest alloy and two different Fe sites in the partially disordered Fe 50Rh 50. Our analysis allowed us to describe the nn atomic arrangements around these sites.

Effects of accelerated eruption on the enamel of the rat lower incisor.

The effect of accelerated eruption of the rat lower incisor on enamel was studied in a series of segments obtained when the incisor was cut repeatedly out of occlusion over a five-week period. The segments were ground, cleaned, acid-etched, observed with SEM, and analyzed with EDX. Pigmentation was lost within 11 days. Pigmented superficial enamel was more acid-resistant than the rest of the enamel, but this quality decreased with decreasing iron content. Hypomineralized enamel first appeared in a restricted area at the mesio-labial angle of the tooth in the 6th-7th segment obtained after 11-14 days. Later, hypomineralization became more generalized. All enamel zones were retained throughout the experiment. The geometry of the prism pattern was affected. The angle between prism rows and the enamel-dentin junction increased from 44 degrees to 48 degrees, while the angle of decussation increased from 60 degrees to 70 degrees. The angle between the enamel surface and prisms in the outer enamel was more difficult to assess, but tended to increase from about 25 degrees to 29 degrees. However, the prisms retained their incisal direction. The connection between enamel and dentin was partly disrupted from about the 9th segment onward. The depth of the mesial concavity of the enamel-dentin junction decreased from about the 10th segment onward. Accelerated eruption affects all stages of enamel formation and is a suitable and predictable model for studying regulatory mechanisms in amelogenesis.

Alteration of Mica and Chlorite in Paddy Soils Derived From Triassic and Jurassic Sediments.

The alteration of mica, chlorite and their related mineral in parent rocks from two terrains being the Middle Triassic to the Middle Jurassic was discussed in two paddy fields of Gray Lowland soils located in Fukui Prefecture. Mica hardly altered to other mineral, but lost iron from its layer lattice and its crystallinity degraded a little in both two soils. Mica-vermiculite interstratified mineral in the Mino Terrain altered to vermiculite. Iron-rich chlorite in the Tanba Terrain changes partially to chlorite-vermiculite intergrade with the decrease of iron from its layer lattice. The alteration of these minerals was due to the decrease of iron content, the decrease of layer charge and the degradation of crystal structure, through the pedogenesis under the seasonally reductive condition.

Influence of carbon introduced by arc melting on the structural and magnetic properties of RFe 12− xV x (R = Y and Dy)

Carbon was introduced by arc melting into RFe 12− x V x compounds, where R = Y or Dy and x = 2, 3 or 4, and its effects on the crystallographic and magnetic properties of these intermetallics were investigated by X-ray, magnetostatic and Mössbauer effect measurements. Experimental results show that the carbon atoms prefer the 4d sites to the 2b sites, or occupy the sites reserved for Fe atoms in the ThMn 12-type crystal structure. Carbon solution increases with increasing vanadium concentration, giving rise to an effect opposite to that of vanadium. An increase in vanadium content causes an increase in the cell volume and a linear decrease in Curie temperature and in the Fe magnetic moment, whereas the addition of carbon leads to a reduction in unit volume while maintaining a high T c and enhancing the Fe magnetic moment despite decreasing iron content in the samples.

The effect of temperature and Fe: Al ratio on the flow and fracture of FeAl

Mechanical testing of large-grained binary FeAl alloys as a function of temperature showed that the yield stress decreased rapidly from 77 to 300 K, followed by a slower decrease up to 500 K. For iron-rich alloys (⩽45at.%Al), the yield stress exhibited a valley at ~500K and a peak at ~675K before declining rapidly at higher temperatures. The stoichiometric alloys showed the highest yield stress at all temperatures. The ductility of the off-stoichiometric alloys in vacuum increased with increasing temperature until at 900 K elongations up to ~150% were obtained; the reduction in area showed a sharp transition from <10% below 500 K to > 80% above 600 K. All off-stoichiometric alloys displayed a mixture of intergranular fracture plus transgranular cleavage below 600 K; the amount of cleavage increased with both decreasing iron concentration and increasing temperature. At temperature ⩾600K the fracture mode changed to ductile rupture.

Energy Metabolism Derangement of the Hepatic Tissue Following Severe Iron Restriction to Rats and its Recovery by Iron Therapy

The effect of severe iron deficiency on hepatic energy metabolism of the rat and of an oral therapy with an iron-protein complex (1TF 1096) on the same parameters has been studied. Severe iron deficiency was induced in rats by rearing nursing dams and their offspring on a diet lacking in iron. The iron-deficient 5-week-old rats exhibited severe anemia and a drastic decrease in iron content of the hepatic tissue and of the mitochondrial fraction. A large increase in liver lipid concentration was observed in iron-deficient animals, whereas there was no modification in the lipid composition of mitochondrial membranes. Mitochondria from anemic rats presented a partial and reversible uncoupling of the oxidative phosphorylation process. The energy state of the liver, as assessed by 31P-NMR spectroscopy, appeared dramatically decreased under this pathological condition. Iron therapy, for 1 week, almost completely corrected severe anemia and the level of iron either in the hepatic tissue or in the mitochondrial fraction. Moreover, iron supplements significantly decreased the abnormal level of liver total lipids and serum triglycerides. In parallel, iron repletion fully reverted both the partial loss of coupled function in isolated mitochondria and the energy state perturbation of the liver.

Dietary iron deficiency in the rat. I. Abnormalities in energy metabolism of the hepatic tissue

Severe iron deficiency was induced in rats by rearing nursing dams and their offspring on a diet comprising all the requisite nutrients and trace metals except iron. The iron deficient 5-week-old rats exhibited a severe anemia and a drastic decrease in iron content of the hepatic tissue and of the mitochondrial fraction. Cytochromes c + c 1 and b were moderately but significantly reduced. A large increase in liver lipid concentration was observed in iron-deficient animals; whereas there was no modification in total lipid, cholesterol, phospholipid and fatty acid composition of the mitochondrial membrane. Mitochondria from iron-deficient rats presented a partial uncoupling of the oxidative phosphorylation process. This functional derangement was completely reversed by the presence of either bovine serum albumin or l-carnitine plus ATP. This behaviour suggested that endogenous long-chain fatty acids could be primarily involved in the onset of mitochondrial dysfunction. The hepatic energy state of the liver appeared dramatically decreased under the pathological condition of severe iron-deficiency anemia. The possibility of a direct link between the partial loss of coupled functions observed in isolated mitochondria and the heavy energy deficit detected in the liver is discussed.

Studies of the stoichiometrical variation of epitaxial Fe/sub 3(1-δ)/O/sub 4/ thin films

Using plasma-assisted molecular beam epitaxy, (MBE) films of iron oxide spinel phases of Fe/sub 3(1-/spl delta/)/O/sub 4/ type have been grown on single crystal MgO(100). Stoichiometry was controlled by variation of growth parameters, including substrate temperature, oxygen flux, plasma power, and deposition rate. Structural and magnetic studies of these films have been performed using SQUID magnetometry and X-ray diffraction (XRD), The temperature dependence of the Verwey transition, a strong indicator of iron oxide stoichiometry which occurs in Fe/sub 3/O/sub 4/ at /spl sim/123 K, is broadened and pushed downward in temperature with decreasing iron content (and is absent in /spl gamma/-Fe/sub 2/O/sub 3/). Lattice spacing, Verwey response, and magnetic ordering show that stable growth over a broad range of conditions results in stoichiometric Fe/sub 3/O/sub 4/, although variation of growth parameters (especially high O/sub 2//Fe flux ratios) can produce a range of Fe/sub 3(1-/spl delta/)/O/sub 4/ "defect-spinels".< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Phase relations in the Fe-Zn-S system to 5 kbars and temperatures between 325 degrees and 150 degrees C

Sphalerite, pyrite, and pyrrhotite were recrystallized together in a saturated ammonium iodide solution at 150 degrees to 325 degrees C and 0.4 to 5.1 kbars. The data were obtained from ten sets of experiments comprising gold capsules stacked consecutively within the bores of cold seal pressure vessels which were heated for periods of between 300 and 750 days. Five capsules contained magnetite as an additional reactant.A P-T-composition map has been constructed for sphalerite buffered by pyrite and hexagonal pyrrhotite. The upper P-T range for the present study includes the lower temperature boundary for the sphalerite geobarometer which has been located near 285 degrees C at 0.5 kbars and 300 degrees C at 5 kbars. The provisional lower P-T range for the present data extends from approximately 180 degrees C at 0.5 kbars to 190 degrees C at 5 kbars. Within the investigated P-T interval, isobaric composition curves for sphalerite show a progressive decrease in iron content with increasing pressure and decreasing temperature.Hexagonal pyrrhotite was the only iron monosulfide identified in the experimental reaction products and was found to increase in iron content with increasing pressure. Its occurrence in these long-term experiments supports earlier predictions that monoclinic pyrrhotite may be a metastable phase down to low temperatures. Hexagonal pyrrhotite may stably invert to monoclinic pyrrhotite at temperatures below 150 degrees C under isotropic stress conditions; however, at higher temperatures monoclinic pyrrhotite appears to be favored by anisotropic stress conditions which produce lattice strain. Under these conditions it may form and persist metastably as the preferred phase below the sphalerite geobarometer boundary. The presence of magnetite does not affect the compositions of sphalerite or pyrrhotite under the conditions of study.The present calibration may be applied to hydrothermal vein deposits provided codeposition of phases can be proven; however, it is expected to have limited application for massive sulfide ores that have prograded or retrograded to temperatures around or below 300 degrees C. This is because the calibration requires buffering by pyrite and hexagonal pyrrhotite, whereas most lower temperature assemblages appear to have been buffered by pyrite and monoclinic pyrrhotite over a range of temperatures, pressures, and anisotropic stress conditions. This latter buffer has restricted sphalerite compositions between around 11 and 12 mole percent FeS.

Iron chromium antimonates and iron gallium antimonates: preparation, structural and magnetic properties

New mixed oxides of composition Fe 1− x Cr x SbO 4 and Fe 1− x Ga x SbO 4 have been prepared. New X-ray powder diffraction data for the compound GaSbO 4 are presented and the decrease in lattice parameters of FeSbO 4 when Fe 3+ is substituted by smaller Cr 3+ or Ga 3+ ions is discussed. The temperature dependence of the inverse magnetic susceptibility of Fe 1− x Cr x SbO 4 at temperatures exceeding ca 200 K follows a Curie-Weiss law. The Curie temperatures and effective magnetic moments decrease with decreasing iron content and are consistent with the substitution of Fe 3+ by Cr 3+ and a reduction in magnetic interaction between cations in the solid. Deviations from the Curie-Weiss law occur at lower temperatures with increasing chromium content and reflect the effect of chromium on the formation of clusters with short-range magnetic order amongst the Fe 3+ species. A second Curie-Weiss law at even lower temperatures and a maximum in the magnetic susceptibility data recorded from Fe 0.85Cr 0.15SbO 4 and Fe 0.63Cr 0.37SbO 4 between 30 and 10 K is indicative of a spin glass-type transition in these materials. The trends in magnetic properties of materials of the type Fe 1− x Ga x SbO 4 are similar, but more marked as a result of the substitution of paramagnetic Fe 3+ by diamagnetic Ga 3+. The 57Fe Mössbauer spectra recorded from Fe 1− x Cr x SbO 4 and Fe 1− x Ga x SbO 4 show an absence of magnetic splitting at 77 K, indicative of faster relaxation times than occur in FeSbO 4. The 121Sb Mössbauer spectra recorded at low temperature show evidence for a super-transferred hyperfine magnetic field on the Sb 5+ ion from iron via oxygen in the iron-rich mixed oxides.