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The magnetization of Fe/Si multilayers, grown by thermal evaporation in an ultrahigh vacuum system, was investigated at high temperatures. Magnetization and its temperature dependence up to a high temperature of 800 K depend on individual Fe layer thickness dFe. This dependence is the result of the formation of an Fe–Si interface layer (nonmagnetic phase) during the synthetic procedure. The fraction of this Fe–Si nonmagnetic phase is estimated versus dFe. At temperatures higher than 400 K an irreversible decrease in the magnetization occurs. A quantitative analysis of this irreversible behavior is proposed in terms of an exponential diffusion-like kinetic equation for the reaction that produces the Fe–Si nonmagnetic phase. The coefficients of the rate equation are the activation energy Ea and the prefactor D0, which have been determined for different dFe. [ABSTRACT FROM AUTHOR]

Two new neodymium molecular magnets of formula {[Nd(α-fur)3(H2O)2]·DMF}n (1) and {[Nd0.065La0.935(α-fur)3(H2O)2]}n (2), α-fur = C4H3OCOO, have been synthesized. In (1) the furoate ligands, in bidentate bridging mode, consolidate zig-zag chains running along the a-direction. Compound (2) is a magnetically diluted complex of a polymeric chain along the b-axis. Heat capacity, dc magnetization and ac susceptibility measurements have been performed from 1.8 K up to room temperature. Ab initio calculations yielded the gyromagnetic factors gx* = 0.52, gy* = 1.03, gz* = 4.41 for (1) and gx* = 1.35, gy* = 1.98, gz* = 3.88 for (2), and predicted energy gaps of Δ/kB = 125.5 K (1) and Δ/kB = 58.8 K (2). Heat capacity and magnetometry measurements agree with these predictions, and confirm the non-negligible transversal anisotropy of the Kramers doublet ground state. A weak intrachain antiferromagnetic interaction J′/kB = −3.15 × 10−3 K was found for (1). No slow relaxation is observed at H = 0, attributed to the sizable transverse anisotropy component, and/or dipolar or exchange interactions enhancing the quantum tunnelling probability. Under an external applied field as small as 80 Oe, two slow relaxation processes appear: above 3 K the first relaxation mechanism is associated to a combination of Orbach process, with a sizeable activation energy U/kB = 121 K at 1.2 kOe for (1), Raman and direct processes; the second, slowest relaxation mechanism is associated to a direct process, affected by phonon-bottleneck effect. For complex (2) a smaller U/kB = 61 K at 1.2 kOe is found, together with larger g*-transversal terms, and the low-frequency process is quenched. The reported complexes represent rare polymeric Nd single-ion magnets exhibiting high activation energies among the scarce Nd(III) family. [ABSTRACT FROM AUTHOR]

We report the synthesis, crystal structure and magnetic properties of a new heteronuclear polymeric complex based on non-Kramers Tb ions and carboxylic α-fur = C4H3OCOO ligands: {[Tb2Ba(α-fur)8(H2O)4]·2H2O}n. The α-furoate ligands consolidate 1D zig-zag chains running along the c-axis, formed by Tb2 dimers separated by Ba ions. Ab initio calculations, in combination with the fit of experimental data, predict that the single-ion magnetic ground state is highly anisotropic (UGRAPHIC DISPLAY="INLINE" ID="UGT1" SRC="UGT1"/) and consists of a quasi-doublet with a ΔTb/kB = 3.22 K gap, well separated from the next excited state, while the gap for the Tb2 dimer is Δ2Tb/kB = 2.58 K. Static magnetization and heat capacity measurements show that, magnetically, the system can be modeled as dimers of non-Kramers Tb ions, coupled by an antiferromagnetic intradimer interaction J′*/kB = −1.6 K. Dipolar interactions couple the Tb ions in the dimer with their first neighbour ions along the chain, with J′′*/kB = −0.15 K, and with the surrounding ions out of the chain, with maximum J′′′*/kB = −0.03 K. Ac susceptibility measurements in H = 0 performed down to 50 mK temperatures have enabled us to observe slow relaxation of magnetization, with an Orbach-like activation energy of U/kB = 1.1 K. It is assigned to the sluggish response of the 3D spin system due to a short-range ordering, possibly enhanced by the presence of disorder caused by defects in the polymeric chains. Under the application of a magnetic field, the system slowly relaxes by two distinct direct processes, strongly affected by a phonon bottleneck effect. We discuss the different relaxational phenomenology of the new complex in comparison with that of the isostructural {[Dy2Ba(α-fur)8(H2O)4]·2H2O}n, differing only in the Kramers nature of the ions, and the mononuclear {Ln(α-fur)3(H2O)3}n (Ln = Tb, Dy) complexes, previously reported. [ABSTRACT FROM AUTHOR]

The objective of the study was to evaluate pregnancy rate per fixed-time artificial insemination (P/FTAI) in suckled beef cows treated with a progesterone intravaginal device (IVD) and two different doses of estradiol cypionate (ECP).The study included Angus suckled cows (n=949), with 45 to 80 postpartumdays and a range of body condition score (BCS) from 3 to 8 (scale 1 to 9). All cows belonged to the same commercial farm in the west of the Buenos Aires Province in Argentina and were grazing consociated pastures (based on Alfalfa). On Day 0, replicate, BCS and ciclicity (by trans rectal examination) was recorded. Cows were synchronized with a protocol including 2 mg of estradiol benzoate and an IVD with 1 g of progesterone on Day 0. On Day 7.5-8 cows received 0.5 mg Cloprostenol and the IVD was removed, and cows considered non cyclic on Day 0 also received 400 IU of eCG at IVD removal. On this day, cows were randomly assigned to receive 0.5 or 1 mg of ECPfor induction of ovulation and were FTAI between 50 to 55 h later, using frozen / thawed semen from a bull of proven fertility.The effect of treatment and other variables on P/FTAI was evaluated using multiple logistic regression (STATA / IC 14.2, StataCorp LP, 4905 Lakeway Drive, College Station, Texas 77845 USA).There was no effect of ECP treatment on P/FTAI) pregnancyper FTAI (0.5 mg: 67.2% y 1 mg: 71.9%; P = 0.11). There was a significant effect of replicate(P <0.01) and there was no significant effect of BCS, ciclicty and their interactions. It is concluded that the dose of ECP (0.5 mg vs 1 mg) can be used indistinctly to induce ovulation in beef cows. [ABSTRACT FROM AUTHOR]

Conception rates using protocols for timed artificial insemination (TAI) with an intravaginal device (ID) containing 1.0 or 3.0 g of progesterone (P4) combined with one dose of 0.30 mg or two doses of 0.15 mg of D-cloprostenol given 24 h apart (2x2 factorial) were compared in dairy cows. Cows (n= 336) received 10 µg of buserelin and anID of 1.0 or 3.0 g of P4 on Day -10, removal of ID and one dose of D-cloprostenol on Day -3 or double doses (Days -3 and -2). Cows in estrus were artificially inseminated (AI) between Days -3 and -1 and cows that were not AI received 10 µg of buserelin and were TAI on Day 0. Conception rates were 25.3 (41/162) and 30.5% (53/174) for ID containing 1.0 and 3.0 g of P4 respectively (p= 0.3); and 25.3 (42/166) and 30.6% (52/170) for one or two doses of D-cloprostenol respectively (p= 0.3). Conception rates were higher for cyclic cows (p= 0.05), primiparous (p= 0.05) and AI on estrus (p= 0.02).Type of P4 device x ciclicity interaction on pregnancy rate was detected (p= 0.05). A higher conception rate for “anovulatory" cows treated with an ID of 3.0 g of P4 (29.7%) than for cows treated cows with an ID of 1,0 g of P4 (11.1%) was observed (p= 0.05); however, in “normal" cows, no significant difference was observed in the conception rate between type of ID (30.7 and 30.8%, respectively). It is concluded that an ID with higher amount of P4 could be more effectiveon anestrus dairy cows. [ABSTRACT FROM AUTHOR]

We have experimentally characterized the magnetization processes of a square array of micron sized circular antidots lithographed on a Fe(001)/GaAs film with its diagonals along the Fe magnetocrystalline easy axes (100). Both the anisotropy and the angular dependence of the magnetization reversal were measured by means of magnetooptic techniques. The coercivity of the loops along the easy and in-plane hard axes of the array increases approximately 2.5 times with respect to that measured in the continuous film region, and the first order anisotropy constant remains equal to that of bulk Fe. The magnetization reversal takes place in two steps for all the loops measured out of the easy and hard axes. We have simulated the magnetization reversal using two different micromagnetic models. In the first one, assuming that the reversal takes place fully inside the array, we have observed that the reversal nucleates at the magnetic inhomogeneities occurring at the antidot boundaries and resulting from magnetostatic energy minimization. In our second model we artificially introduced a domain wall outside the antidot region that governs the magnetization reversal showing a qualitative agreement with the angular dependence of coercivity. [ABSTRACT FROM AUTHOR]

Field-cooled x-ray magnetic circular dichroism experiments at several temperatures at the Mn K and Nd L2,3 edges on nonstoichiometric NdMnO3.11 have been performed. Our results show that Nd and Mn net magnetizations are parallel along the whole range of temperatures, ruling out the competition between the Nd and Mn sublattices as the origin of negative magnetization in NdMnO3+Δ. [ABSTRACT FROM AUTHOR]

The study of ratchet and crossed-ratchet effects in magnetic domain wall motion through 2D arrays of asymmetric holes is extended in this article to the submicrometric limit in hole size (small size regime). Therefore, the gap has been closed between the 2D ratchets in the range of tens-of-micrometers (large size regime) and the small size regime 1D ratchets based on nanowires. The combination of Kerr microscopy, X-ray PhotoEmission Electron Microscopy and micromagnetic simulations has allowed a full magnetic characterisation of both the domain wall (DW) propagation process over the whole array and the local DW morphology and pinning at the holes. It is found that the 2D small size limit is driven by the interplay between DW elasticity and half vortex propagation along hole edges: as hole size becomes comparable to DW width, flat DW propagation modes are favoured over kinked DW propagation due to an enhancement of DW stiffness, and pinned DW segments adopt asymmetric configurations related with Néel DW chirality. Nevertheless, both ratchet and crossed-ratchet effects have been experimentally found, and we propose a new ratchet/inverted-ratchet effect in the submicrometric range driven by magnetic fields and electrical currents respectively. [ABSTRACT FROM AUTHOR]

Multilayers of bimetallic CoPd alloyed and assembled nanoparticles, prepared by room temperature sequential sputtering deposition on amorphous alumina, were studied by means of high-resolution transmission electron microscopy, x-ray diffraction, SQUID-based magnetometry and x-ray magnetic circular dichroism. Alloying between Co and Pd in these nanoparticles gives rise to a high perpendicular magnetic anisotropy. Their magnetic properties are temperature dependent: at low temperature, the multilayers are ferromagnetic with a high coercive field; at intermediate temperature the behavior is of a soft-ferromagnet, and at higher temperature, the perpendicular magnetic anisotropy in the nanoparticles disappears. The magnetic orbital moment to spin moment ratio is enhanced compared with Co bare nanoparticles and Co fcc bulk. [ABSTRACT FROM AUTHOR]

The magnetization contributions of the Fe 3 and Ln subcluster in the “butterfly” molecule [Fe 3 Ln(μ 3 -O) 2 (CCl 3 COO) 8 (H 2 O)(THF) 3 ], in brief {Fe 3 LnO 2 }, with Ln=Lu, Gd, Tb, Dy and Ho, have been determined by a combination of vibrating sample magnetometry and x-ray circular magnetic dichroism at low temperature and magnetic field up to 14 T. These contributions have been explained in terms of an effective spin model where the Fe 3 is described by a S Fe 3 = 5 / 2 spin, Gd by an isotropic J =7/2, Dy by a Kramers doublet, and non-Kramers ions Tb and Ho by a ligand field split doublet. The intracluster interactions J FeLn have been found to amount to a few K. [ABSTRACT FROM AUTHOR]

Magnetic properties of heterometallic warwickites MgFeBO 4, Mg 0.5 Co 0.5 FeBO 4, and CoFeBO 4 are presented, highlighting the effect of Co substitution on the magnetic properties of these compounds. The analysis of magnetization and heat capacity data has shown that these compounds exhibit a spin-glass transition below T SG =10, 20 and 22 K, respectively. Using zero field ac susceptibility as entanglement witness we find that the low dimensional magnetic behavior above T SG show quantum entanglement behavior χ ( Τ )∝ T − α ( Τ ) up to T E ≈130 K. The α parameters have been deduced as a function of temperature and Co content, indicating the existence of random singlet phase in this temperature region. Above T E the paramagnetism is interpreted in terms of non-entangled spins giving rise to Curie–Weiss paramagnetism. The different intra- and inter-ribbon exchange interaction pathways have been calculated within a simple indirect coupling model. It is determined that the triangular motifs in the warwickite structure, together with the competing interactions, induce frustration. The spin-glass character is explained in terms of the substitutional disorder of the Mg, Fe and Co atoms at the two available crystallographic sites, and the frustration induced by the competing interactions. The Co substitution induces uniaxial anisotropy, increases the absolute magnetization and increases the spin-glass freezing temperature. The entanglement behavior is supported in the intermediate phase irrespective of the introduction of anisotropy by the Co substitution. [ABSTRACT FROM AUTHOR]

Single-crystalline MgFeBO4, Mg0.5Co0.5FeBO4, and CoFeBO4 have been grown by the flux method. The samples have been characterized by X-ray spectral analysis, X-ray diffraction, and X-ray absorption spectroscopy. The X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra have been measured at the Fe and Co K-edges over a wide temperature range (6.5-300 K). The composition, the charge state, and local environment of both Fe and Co atoms have been determined. The effects of Co substitution for Mg on the local structural distortions have been revealed experimentally and the MO bond anisotropy has been found. [ABSTRACT FROM AUTHOR]

Single crystals of MgFeBO 4 and СоFeBO 4 warwickites were obtained. The effects of charge ordering and magnetic properties were investigated by Mössbauer spectroscopy. Cation distribution over M1 and M2 nonequivalent sites and the average charge at the metal positions were established. Low temperature Mössbauer spectra reveal spin-glass behavior, with spin-freezing temperatures T SG of 15.2 and 33.2 K for Mg- and Co-warwickites, respectively, higher than that observed from the d.c. and a.c. magnetic susceptibility measurements. The difference is explained in terms of dynamical scaling theory. The specific shape of the Mössbauer spectra in the vicinity of the magnetic transition at T SG shows the difference between spin-glass and superparamagnetic behavior and demonstrates an overwhelming role of the exchange anisotropy in the properties of Mg-warwickite. In Co-warwickite the increase of magnetocrystalline anisotropy provokes an increase in magnetic viscosity. [ABSTRACT FROM AUTHOR]

The temperature dependence of the resistivity of single crystalline Mg 1 − x Co x FeBO 4 samples with x = 0.0, 0.5, 1.0 is investigated for the temperature range (210–400 K). The conduction was found to be governed by Mott variable-range hopping (VRH) in the low-temperature range ( T = 210–270 K) and by thermo-activation mechanism in the high-temperature range ( T = 280–400 K). Microscopic electronic parameters, such as the density of the localized states near the Fermi level, localization length, the hopping length, and the activation energy have been obtained. The change of the activation energy observed at high-temperature range was attributed to local structure distortions around Fe and Co atoms. The complicated behavior of charge transfer mechanisms is discussed based on two approaches: atomic disorder and electron correlations. [ABSTRACT FROM AUTHOR]

A systematic study of the iron–silicon interfaces formed upon preparation of (Fe/Si) multilayers has been performed by combination of modern and powerful techniques. Samples were prepared by thermal evaporation under ultrahigh vacuum onto a Si(1 0 0) substrate. The morphology of these films and their interfaces was studied by a combination of scanning transmission electron microscopy, X-ray reflectivity, angle resolved X-ray photoelectron spectroscopy and hard X-ray photoelectron spectroscopy. The Si-on-Fe interface thickness and roughness were determined to be 1.4(1) nm and 0.6(1) nm, respectively. Moreover, determination of the stable phases formed at both Fe-on-Si and Si-on-Fe interfaces was performed using conversion electron Mössbauer spectroscopy on multilayers with well separated Si-on-Fe and Fe-on-Si interfaces. It is shown that while a fraction of Fe remains as α -Fe, the rest has reacted with Si, forming the paramagnetic c-Fe 1− x Si phase and a ferromagnetic Fe rich silicide (DO 3 type phase). We conclude that the paramagnetic c-Fe 1− x Si silicide sublayer is identical in both Si-on-Fe and Fe-on-Si interfaces, whereas an asymmetry is revealed in the composition of the ferromagnetic silicide sublayer. [ABSTRACT FROM AUTHOR]

The experimental studies on R 3+ Fe 3+ Ti 2 O 7 (R=Sm, Gd, Tb, Tm, Dy) magnetic properties evidence the low temperature spin glass state in all compounds. The possibility of rare-earth cation substitution allows the investigation of the role of magnetic iron Fe 3+ ions and rare earth R 3+ ions subsystems in a ground state formation in these oxide compounds. [ABSTRACT FROM AUTHOR]

The room temperature reaction of [Mn2O2(bipy)4l(ClO4)3 (bipy = 2,2'-bipyridine) with Ca(CHCl2COO)2 in methanol produced a yellow crystalline material. The X-ray determined structure comprises of a multiple calcium(II) carboxylate bridged chain-like structure which is decorated with [Mn(bipy)2(OH2)]2+ subunits. The redox behaviour for the complex in H2O and MeCN is reported. In the latter solvent the oxidation of the manganese ions appears to be facilitated by the presence of the calcium ions. Magnetic susceptibility and low temperature magnetization measurements show that the Mn moment is isotropic, with g = 1.99(1) and S = 5/2, confirming it is in the 2+ oxidation state. A very weak antiferromagnetic interaction is also detected. Frequency-dependent ac measurements evidence slow magnetic relaxation of the Mn(bipy)2 units. Two relaxation mechanisms are identified: a very slow direct process and a faster one caused by the Resonant Phonon Trapping mechanism. This is the first example of field-induced single ion magnet (SIM) behavior in a mononuclear Mn(II) complex. [ABSTRACT FROM AUTHOR]

This work presents the correlation between the morphology and magnetic properties of (Fe/Si)3 multilayers with different Fe layer thicknesses and fixed Si spacer thickness in a broad temperature range ( ). Films were prepared by thermal evaporation under ultrahigh vacuum onto a buffer layer of Fe/Ag deposited on a GaAs(001) substrate. Transmission electron microscopy reveals good epitaxial growth and phase transformations in the c-FeSi phase formed during deposition as well as upon subsequent annealing of the sample up to 800K. Remanence to saturation magnetization M R /M S ratios and saturation fields are related to several types of interlayer exchange coupling. 90°-coupling and a superposition of 90° and antiferromagnetic interlayer exchange coupling are found depending on the Fe layer thickness. Magnetization curves were investigated as a function of temperature by in situ annealing. They show an irreversible thermal process as temperature increases from 300 to 450K that is correlated to the formation of a ferromagnetic silicide phase. At higher temperature this phase transforms into a paramagnetic Fe–Si phase. [ABSTRACT FROM AUTHOR]

The lanthanide(III) cyanoacetate complexes of the formula {[Ln2(CNCH2COO)6(H2O)4]·2H2O}n, where Ln = Eu (1), Gd (2), Nd (3), have been prepared and characterized by X-ray diffraction analysis. Complexes 1 and 2 are isostructural and differ from the binding scheme of the neodymium compound 3, structurally described earlier. In all cases, the cyano group of the cyanoacetate ligand is not coordinated to the lanthanide cation. The carboxylic groups exhibit different binding modes: 2-bidentate-chelating, 2-bidentate and 2-tridentate-chelating bridging for 1 and 2, and 4-bidentate and 2-tridentate-chelating bridging for the complex 3. The Eu compound 1 shows field induced paramagnetism, as expected for a non-magnetic ground state with mixing from higher states. Combining the dc magnetization and luminescence measurements the spin-orbit coupling constant λ = 343 ± 4 cm-1 was found, averaged over the two different sites for Eu in the lattice. In the Gd complex 2, a crystal field splitting of D/kB = -0.11 ± 0.01 K has been found for the S = 7/2 multiplet of the Gd(III) ion. No slow relaxation at H = 0 is observed because the low anisotropy barrier allows fast spin reversal through classical processes. The application of an external magnetic field induces two slow relaxation processes. It is argued that the first relaxation rate is caused by the resonant phonon trapping (RPT) mechanism, while the second, slower relaxation rate is due to the lifting of the Kramers degeneracy on the ground state. For compound 3 heat capacity and dc susceptibility measurements indicate that at very low temperatures the ground state Kramers doublet has strong single ion anisotropy. The energy to the next excited doublet λZFS/kB = 104 K has been calculated by ab initio calculation methods. The g* tensor has also been calculated, showing that it has predominant anisotropy along the z-axis, and there is an important transversal component. At H = 0 quantum tunnelling is an effective mechanism in producing a fast relaxation to equilibrium at temperatures above 1.8 K. The dipolar or exchange interactions and a sizable transverse anisotropy component in the ground state enhance the quantum tunneling probability. Under an external applied field, two slow relaxation processes appear: above 3 K the first relaxation mechanism is of the Orbach type, with an activation energy U/kB = 27 K; the slower relaxation is caused by the direct relaxation process from the ground state to the Kramers split levels by the applied field. [ABSTRACT FROM AUTHOR]

Permalloy antidot thin films were grown by sputtering onto anodic alumina templates, replicating their hexagonal order inside micrometric geometric domains. The advanced high-spatial and sensitive x-ray photoemission electron microscopy technique under an applied magnetic field has enabled magnetic domain structure imaging and quantitatíve hysteresis loop analysis inside nanoscale regions with geometric order and at border regions. The study has been complemented by vibrating sample magnetometry and magneto-optic Kerr effect measurements. The magnetization process is clearly determined by the geometry characteristícs of the antidot arrays. Inside geometric ordered domains, the strength of effectíve in-plane magnetic anisotropy depends on the antidot diameter-to-film thickness ratio, which determines the partial balance between stray fields generated by magnetic charges at the lateral surface of the antidots and those at the upper-bottom film surface. In addition, the border regions between geometric domains act as pinning centers for magnetization reversal and eventually generate a harder magnetic region. [ABSTRACT FROM AUTHOR]

Abstract: We report results of a powder neutron diffraction study on the crystal structure and local magnetic moments in Nd3Co13− x Ni x B2 compounds with Nd3Ni13B2-type structure. The largest 3d magnetic moment resides at the 4h sites. Nd magnetic moment is reduced with respect to the free ion value. Preferential Ni substitution for Co is also found at the 4h site. The refined magnetization direction is consistent with the T–x phase diagram derived from magnetization data. [Copyright &y& Elsevier]

Abstract: Magnetic anisotropy of Co nanoparticles homogeneously dispersed in alumina is increased by capping the particles with copper. In the present work, we investigate this effect by measuring X-ray magnetic circular dichroism (XMCD) at the K and L2,3 edges of Co and Cu atoms. We demonstrate that orbital-to-spin ratio at the Co 3d states is increased by capping with Cu, explaining the observed enhancement of the macroscopic anisotropy. Hybridization between Co and Cu at the interface produces an electronic transfer between them. Clear induced magnetic moments are observed in copper, both in the 4p states and in the 3d states. [Copyright &y& Elsevier]

Abstract: The crystal structure, cation distribution and exchange interactions in the Co2.25Fe0.75O2BO3 ludwigite have been explored through X-ray diffraction, electrical resistivity, ac-susceptibility and Mossbauer effect measurements. The crystal data have shown that iron atoms occupy the most symmetric crystallographic sites Fe4 and Fe2. The complex magnetic behavior with two magnetic transitions near 70 and 115K at low temperatures was found. The Mossbauer data have displayed the trivalent iron states only. The values of superexchange energies have been estimated for Co3O2BO3 and Co2.25Fe0.75O2BO3 yielding a significant role of frustrations in the ludwigite magnetic system. Variable range Mott hopping conductivity law was proved to be valid in the wide temperature region, pointing out a localized character of charge carriers rather than collective. [ABSTRACT FROM AUTHOR]

Abstract: The results of the study of thermodynamic properties of the anisotropic 2H-NbSe2 compound, in the superconducting to normal state (SN) upper critical field HC 2 –TC transition line, and in the charge density wave (CDW) transition are presented. Isothermal heat capacity and magnetization measurements were performed to determine the heat capacity jump at the HC 2–TC transition line. With these results the validity of the Second Ehrenfest relation for this type II superconductor was checked. The temperature dependences of the heat capacity and the thermal expansion along the crystallographic axis с were measured. Both properties manifest the sharp features of BCS-type at the superconducting transition and more diffuse features at the CDW transitions. These results, together with the First Ehrenfest relation, allowed us to estimate the critical temperature derivative on uniaxial pressure applied along the hexagonal axis с, p IIс, . The same methodology has been applied to the CDW transition, where a positive derivative on uniaxial pressure was deduced. [Copyright &y& Elsevier]

Abstract: The heat capacity of the Y3Ni13− x Co x B2 series has been measured from 300mK to RT. The magnetic ordering phase transitions have been characterized as second-order type and the T c''s determined. The electronic contribution to the low-temperature heat capacity for x=0 yields an electronic constant γ=54mJmolK2, which is higher than those of YNi5 and YNi4B, proving experimentally that its density of states at the Fermi surface is larger than in those other compounds. The substitution of Ni by Co increases γ linearly. Electronic band calculations could explain these features. [Copyright &y& Elsevier]

Abstract: The series of compounds RFe11.3W0.7, where R=Dy, Ho, Er, and Lu, has been measured by Mössbauer spectroscopy between 15 and 295K. A model which takes into account the Wigner–Seitz cell local environment of each iron site, the distribution of tungsten atoms on the 8i site, and the temperature-dependent magnetic structures of the compounds has been used to analyse the spectra. The assignment and the temperature dependencies of the hyperfine fields and the isomer shifts are in complete agreement with the Wigner–Seitz cell analysis of the three iron sites in RFe11.3W0.7 compounds. The plausible orientations of the iron magnetic moments in the canted magnetic phase of ErFe11.3W0.7 compound have been established by a thorough Mössbauer spectral analysis. The Mössbauer spectra of DyFe11.3W0.7 clearly show the influence of the two spin re-orientations occurring in this compound and indicate the directions of the iron magnetic moments in both canted and planar magnetic arrangements. [Copyright &y& Elsevier]

Strips containing arrays of submicrometric triangular antidots with a 2D square periodicity have been fabricated by electron beam lithography. A clear ratchet effect of 180° domain wall motion under a varying applied field parallel to the walls has been observed. The direction is determined by the direction of the triangle vertices. In contrast, no ratchet effect is observed when the antidot array is constituted by symmetric rhomb-shaped antidots. [ABSTRACT FROM AUTHOR]

Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by CoPd alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of L10 strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) μB and 0.45(4) μB are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) μB, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the 3d-4d bands associated to the Co and Pd chemical arrangement in a L10 structure type. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of the magnetic ordering of Nd with the Fe content in is studied by low-temperature specific-heat measurements for . The experiments show that Nd ordering takes place for , but it is inhibited for . Fe doping creates a distribution of internal fields on Nd, originating a Schottky contribution to the specific heat which is present for . The power law followed by the low-temperature specific heat suggests a glassy behavior for . [Copyright &y& Elsevier]

Abstract: The 57Fe Mössbauer spectra of (, 0.1, 0.2, 0.25, 0.5 and 0.7) have been measured at room temperature (RT). For the spectra have been fitted with magnetic sextets with their areas following a binomial distribution of Fe surroundings with Ga neighbours. The spectra for and 0.7 show paramagnetic doublets, which account for the percolation effect induced by the non-magnetic Ga substitution for Fe, which has been estimated to be at RT. The analysis of the hyperfine field values as a function of the Ga concentration shows the effect of the variations of the antiferromagnetic sublattice magnetization. Moreover, the dependence of this field with the number of susbstituted neighbours suggests an increase of the average Fe–O–Fe exchange interaction as a consequence of the lattice contraction when Ga susbtitutes for Fe. [Copyright &y& Elsevier]

Objective: Several studies have reported that a higher degree of hemoconcentration in patients admitted for the treatment of acute heart failure (HF) constitutes a favorable prognostic factor in the year following the index episode. The objective of this study was to evaluate whether the highest degree of hemoconcentration at 3 months after admission for HF is also a prognostic factor for mortality and/or readmission in the 12 months after admission., Patients and Method: The hemoconcentration group was the upper quartile of the sample distributed according to hemoglobin increase at month 3 after discharge with respect to hemoglobin at the time of admission for HF in a multicenter prospective cohort of 1,659 subjects with HF., Results: The mean follow-up until the first event was 294 days, and a total of 487 deaths and 1,125 readmissions were recorded. The hemoconcentration group had a lower risk of mortality or readmission for any cause (RR=0.75, 95% CI: 0.51-1.09 and RR=0.86, 95% CI: 0.70-1.05), although statistical significance was lost after multivariate analysis, while it was retained for other factors with recognized negative impact on the prognosis of patients with HF, such as age and functional class., Conclusions: The degree of hemoconcentration at 3 months after admission for HF is not prognostic of readmission or death in the subsequent year., (Copyright © 2018 Elsevier España, S.L.U. and Sociedad Española de Medicina Interna (SEMI). All rights reserved.)

To describe the epidemiology of cystic ovarian disease (COD), to find possible risk factors associated with the incidence of cysts and to analyse the impact of COD on the reproductive performance of dairy cows, databases from 22 dairy herds from the main dairy region in Argentina were retrospectively evaluated throughout a 3-year period (2009-2011). A total of 248 COD cases over 9156 parturitions were recorded, resulting in a cumulative incidence rate of 2.7%. Cystic ovarian disease incidence density was lower during the first 100 days post-partum (DPP) than during later stages of lactation. Seasonality had a significant influence on the disease presentation with higher incidence rates during winter and spring. Cows with a previous diagnosis of clinical mastitis showed 2.72 times more chances of developing ovarian cysts. Cystic cows had longer calving to first service and calving to conception intervals and lower conception rate than controls., (© 2014 Blackwell Verlag GmbH.)