Showing papers on "Metamagnetism published in 2009"
TL;DR: In this article, the authors studied the entropy change and the shift of the martensitic transformation temperatures with magnetic field in samples of a polycrystalline Ni-Co-Mn-In alloy having different degrees of long-range atomic order due to different heat treatments.
Abstract: We studied the entropy change and the shift of the martensitic transformation temperatures with magnetic field in samples of a polycrystalline Ni–Co–Mn–In alloy having different degrees of long-range atomic order due to different heat treatments. We found, for the samples of the same composition, strong variations of the entropy change with the degree of atomic order, mediated by the difference between the Curie and martensitic transformation temperatures. Calculations of the field-induced shift of the transformation using data of entropy variations show good agreement with experimental results.
121 citations
TL;DR: In this paper, a rhombohedrally distorted BiFeO3 structure with compressive lattice distortion induced by the Co substitution at Fe sites from Raman study was obtained.
Abstract: Bi(Fe0.95Co0.05)O3 bulk ceramics were prepared by rapid sintering using sol-gel derived fine powders. Bi(Fe0.95Co0.05)O3 crystallized in a rhombohedrally distorted BiFeO3 structure with compressive lattice distortion induced by the Co substitution at Fe sites from Raman study. Compared with BiFeO3 prepared under similar conditions, the magnetic properties were significantly enhanced, with saturate magnetization of 1.6 emu/g and remnant magnetization of 0.7 emu/g at 300 K. Clear metamagnetism was observed in Bi(Fe0.95Co0.05)O3.
111 citations
TL;DR: Martensitic and magnetic properties of Fe-Mn-Ga single and polycrystalline alloys were investigated in this article, and it was found that Fe-mn-ga alloys exhibit martensitic transformation from the paramagnetic L21 Heusler parent phase to the ferromagnetic L10 martensite phase.
Abstract: Martensitic and magnetic properties of Fe–Mn–Ga single and polycrystalline alloys were investigated. It was found that Fe–Mn–Ga alloys exhibit martensitic transformation from the paramagnetic L21 Heusler parent phase to the ferromagnetic L10 martensite phase. The martensitic transformation temperatures increased by about 20 K by the application of a magnetic field of 7 T, and a metamagnetic phase transition was observed. In addition, a magnetic field-induced strain of 0.6% associated with magnetic field-induced forward transformation was confirmed in an Fe43Mn28Ga29 single crystal.
97 citations
TL;DR: A novel 2D coordination polymer consisting of ferromagnetic Ni(ii) chains with alternating double EO-azid bridges and (EO-azide)bis(carboxylate) triple bridges exhibits solvent-modulated metamagnetism and the reversible dehydration/hydration processes are accompanied by significant changes in critical temperature, critical field and hysteresis.
94 citations
TL;DR: Taking into account the strong anisotropy of the systems and the interlayer dipolar interactions, the unusual metamagnetic and hysteresis behaviors and the differences between 1 and 2 have been reasonably interpreted.
Abstract: The crystal structures and magnetic properties of two new Co(II) molecular magnets, [Co(N(3))(2)(btzb)] (1) and [Co(N(3))(2)(btze)(2)] (2), are described and discussed (btzb=1,4-bis(tetrazol-1-yl)butane and btze=1,4-bis(tetrazol-1-yl)ethane). In the materials, (4,4) layers with mu-1,3-azide bridges are cross-linked by the monolayered btzb bridging ligands or spaced by bilayered btze terminal ligands to give a 3D (1) or 2D (2) coordination network with significantly different interlayer separations (10.6 vs. 15.2 A). The observation that the layers in 1 and 2 are almost identical have not only allowed us to determine how the interlayer separation imposes its influences on their magnetic behavior, but also helps us understand the complex magnetic behavior of each structure. In the high-temperature range (>25 K), almost identical magnetic behaviors, typical of 2D antiferromagnetic systems, are observed for 1 and 2. At low temperature they exhibit unusual and different behaviors that combine spin canting (weak ferromagnetism), metamagnetism, and stepped hysteresis. It has been found that the interlayer separation has little influence on the ordering temperature (23 vs. 22 K), but imposes very-strong influence on the metamagnetic critical field (6500 vs. 450 Oe), the coercivity (7500 vs. 650 Oe), and the hysteresis-step size. It may also play an adjusting role in determining the canting angle. Taking into account the strong anisotropy of the systems and the interlayer dipolar interactions, we have reasonably interpreted the unusual metamagnetic and hysteresis behaviors and the differences between 1 and 2. In particularly, the stepped hysteresis loops have been explained by two weak ferromagnetic states.
94 citations
TL;DR: Inverse and direct magnetocaloric properties were evaluated in preferentially textured Mn50Ni40In10 ribbons applying the magnetic field H∥ along the ribbon length and perpendicular H⊥ to the ribbon plane as discussed by the authors.
Abstract: Inverse and direct magnetocaloric properties were evaluated in preferentially textured Mn50Ni40In10 ribbons applying the magnetic field H∥ along the ribbon length and perpendicular H⊥ to the ribbon plane (ΔH=30 kOe). Maximum magnetic entropy change, hysteretic losses, and refrigerant capacity were not significantly affected by crystallographic texture. Refrigeration capacity around structural transition is strongly reduced by the large hysteretic losses associated to the metamagnetic field-induced reverse martensitic transformation and narrower working temperature range making the interval around the magnetic transition more efficient for a refrigerant cycle (RCstruct=71 J kg−1 versus RCstructeff≈60 J kg−1, and RCmagn=89–86 J kg−1, for H∥ and H⊥, respectively).
93 citations
TL;DR: In this paper, measurements of the anisotropic magnetization and magnetoresistance on single crystals of EuFe2As2, a parent compound of ferro-arsenide high-temperature superconductor, were reported.
Abstract: We report the measurements of the anisotropic magnetization and magnetoresistance (MR) on single crystals of EuFe2As2, a parent compound of ferro-arsenide high-temperature superconductor. Apart from the antiferromagnetic (AFM) spin density wave (SDW) transition at 186 K associated with Fe moments, the compound undergoes another magnetic phase transition at 19 K due to AFM ordering of Eu2+ spins (J=S=7/2). The latter AFM state exhibits metamagnetic (MM) transition under magnetic fields. Upon applying magnetic field with H∥c at 2 K, the magnetization increases linearly to 7.0 μB f.u.−1 at μ0H=1.7 T and then remains at this value for saturated Eu2+ moments under higher fields. In the case of H∥ab, the magnetization increases step-like to 6.6 μB f.u.−1 with small magnetic hysteresis. An MM phase was identified with the saturated moments of 4.4 μB f.u.−1. The MM transition accompanies negative in-plane MR, reflecting the influence of Eu2+ moments ordering on the electrical conduction of FeAs layers. These results were explained in terms of spin-reorientation and spin-reversal based on an A-type AFM structure for Eu2+ spins. The magnetic phase diagram has been established.
81 citations
TL;DR: In this article, the unit cell of the Bi1-xLax FeO3 system is described with the R3c space group in the concentration interval 0.05 and the mixed-phase state was observed in the range 1.5 020, whereas no evidence for Imma phase was found.
Abstract: Crystal structures of Bi1–xLnx FeO3 systems (Ln = La, Nd, Eu) are studied using X-ray and neutron diffraction, magnetization measurements as well as electron microscopy It was shown that the unit cell of the Bi1–xLax FeO3 system is described with the R3c space group in the concentration interval 0 05 The mixed-phase state was observed in the range 015 020, whereas no evidence for Imma phase was found The magnetization study has revealed the spontaneous magnetization to be associated with Pnma and Imma phases that do not allow conventional ferroelectricity The ferroelectric R3c phase exhibits metamagnetic behavior due to transition from an incommensurately modulated antiferromagnetic state to a weak ferromagnetic state Substitution of Bi3+ with Ln3+ leads to a strong decrease of external magnetic field inducing a metamagnetic transition (© 2009 WILEY-VCH Verlag GmbH & Co KGaA, Weinheim)
78 citations
TL;DR: In this article, the inclusions of mesocopic platelets of Gd5Si1.5Ge2 have been shown to seed the global metamagnetic transition to the ferromagnetic state.
Abstract: Metamagnets are materials with first-order phase transition from one magnetically ordered phase to another that could provide environmentally friendly, highly efficient refrigeration near ambient temperatures using a phenomenon known as the magnetocaloric effect. Profoundly important to fundamental research and the application of room-temperature magnetic refrigeration (a solid-state cooling method that takes advantage of the entropy change associated with changes in magnetic order), is the need to understand how the metamagnetic transition evolves, and whether it can be manipulated by nanoengineering, or chemical substitutions to be sharper, occur at a lower magnetic driving fields, or be less hysteretic. Here, using Hall probe imaging, we show that inclusions of mesocopic platelets of Gd5Si1.5Ge1.5, that are inherent to all single crystals and polycrystals of this compound, seed the global metamagnetic transition to the ferromagnetic state across the Gd5Si2Ge2 crystal. We show that these inclusions, as well as well-defined mosaic boundaries, play a dramatic role on the transition properties. Strain and the associated field-driven volume changes underpin the phenomena that we have observed, and show that nanostructuring is the likely route to a more complete control of the critical properties in these materials. Themagnetic cooling field has a historic past, first conceived in the 1920’s by P. Debye and W. Giauque; the concepts have been used to reach extremely low temperatures in a process known as adiabatic demagnetization. Over the past ten years, the field has experienced a resurgence of interest after the discovery of giant magnetocaloric effects in a family of materials known as metamagnets, which are compounds that undergo a first-order transition to a magnetically ordered state, often accompanied by a coincident transformation of the crystal structure. Gd5Si2Ge2 has attracted a great deal of interest in this important area because it could play a pivotal role for energy-efficient magnetic cooling near room temperatures. It is a paramagnet (PM) above 274K with a monoclinic crystal structure; by applying a magnetic field, the material can be converted to a ferromagnetic (FM) state with a different, yet closely related, orthorhombic structure via a first-order transition. It has been shown that alloying Gd5Si2Ge2 with different elements substituting for either Si and Ge, or Gd can tune the critical temperature,Tc, but this leads to a significant shift in the magnetic character from first-order towards second-order behavior, which has an adverse effect on the magnitude of the magnetocaloric effect. Although these are interesting facts, it is true to say that a proper fundamental understanding of how to engineer the metamagnetic transition to optimize the magnetocaloric effect has yet to be established. Conventional structural characterization techniques, such as scanning and transmission electron microscopies (SEM, TEM), and X-ray diffraction have proved to be vitally important for understanding of the Gd5Si2Ge2 compound. High-resolution TEM has shown that all the Gd5Si2Ge2 crystals have a complex microstructure consisting of a dominant matrix of the singlephase parent material that is interspersed with extremely thin-plates (200 nm thick) of a second phase Gd5(SixGe1–x)3 material. In this sense the crystals are not pure, but single-crystal-like diffraction patterns are observed by backscatter Laue technique, and so for all intents and purposes these samples can indeed be considered single crystals. The platelets arrange themselves in a criss-cross pattern when viewed perpendicular or nearly perpendicular to the [010] face (see Fig. 1), with platelets extending for several hundred micrometers. When viewed perpendicular to both the [100] and [001] faces, the platelets
63 citations
TL;DR: In this paper, the influence of the substitution by Fe atoms on the magnetocaloric and magnetic properties of the martensitic Ni50Mn36Sn14 Heusler-type compound has been investigated using magnetization measurements.
Abstract: The influence of the Mn substitution by Fe atoms on the magnetocaloric and magnetic properties of the martensitic Ni50Mn36Sn14 Heusler-type compound has been investigated using magnetization measurements. The insertion of Fe atoms reduces the Mn-Mn AF interactions resulting in (i) a systematic decrease in the martensitic transition temperature, down to its disappearance at 15 at. % of Fe, (ii) an enhancement of the saturation magnetization, and (iii) a monotonic increase in the L21-type phase Curie temperature. The Fe substitution also induces metamagnetic transition from an incipient AF to a noncollinear spin configuration for applied magnetic fields higher than 3 T in the case of 3 and 7 at. % Fe substitutional. The exchange-bias effect is only found in compounds with a well-defined martensitic phase transition (Fe content lower than 10 at. %). The maximum of the inverse magnetic entropy change, for a field variation of 5 T, is about +12 J kg−1 K−1 and it is nearly constant for Fe content up to 7 at. %....
55 citations
TL;DR: In this article, the mechanism of how critical end points of the first-order valence transition (FOVT) are controlled by a magnetic field is discussed, and it is shown that critical temperature is suppressed to be a quantum critical point (QCP) by magnetic field.
Abstract: The mechanism of how critical end points of the first-order valence transition (FOVT) are controlled by a magnetic field is discussed. We demonstrate that critical temperature is suppressed to be a quantum critical point (QCP) by a magnetic field. This results explain the field dependence of the isostructural FOVT observed in Ce metal and YbInCu 4 . Magnetic field scan can make the system reenter in a critical valence fluctuation region. Even in intermediate-valence materials, the QCP is induced by applying a magnetic field, at which magnetic susceptibility also diverges. The driving force of the field-induced QCP is shown to be a cooperative phenomenon of the Zeeman effect and the Kondo effect, which creates a distinct energy scale from the Kondo temperature. The key concept is that the closeness to the QCP of the FOVT is vital in understanding Ce- and Yb-based heavy-fermions. This explains the peculiar magnetic and transport responses in CeYIn 5 (Y=Ir, Rh) and metamagnetic transition in YbXCu 4 for X=In...
TL;DR: In this paper, the high-field magnetization and de Haas-van Alphen (dHvA) oscillations for YbIr 2 Zn 20 with a cubic crystal structure, together with the electrical resistivity and magnetic susceptibility were measured.
Abstract: We measured the high-field magnetization and de Haas–van Alphen (dHvA) oscillations for YbIr 2 Zn 20 with a cubic crystal structure, together with the electrical resistivity and magnetic susceptibility. The magnetic susceptibility χ with an effective magnetic moment of Yb 3+ becomes temperature-independent at low temperatures, with a broad peak at T χmax =7.4 K for H ∥ . The corresponding magnetization indicates a metamagnetic transition at H m =120 kOe, consistent with a T χmax vs H m relation in the Ce- and U-based heavy fermion compounds. The large cyclotron masses of 4–27 m 0 are detected in the dHvA experiment, and are found to be reduced at magnetic fields higher than H m =120 kOe. The resistivity follows the Fermi liquid relation ρ=ρ 0 + A T 2 under magnetic field, and the \(\sqrt{A}\) value is also found to have a maximum at H m as a function of magnetic field. From the present experimental results, together with the results of 4 f -itinerant energy band calculations, the 4 f electrons are fou...
TL;DR: At temperatures below 5 K the field dependence of the magnetization of the pi-stacked bis-dithiazolyl radical 1 (R(1) = Me, R(2) = H) is consistent with metamagnetic behavior.
TL;DR: In this article, the thermal history-dependent (THD) isothermal magnetoresistance (MR) behavior of Ni49.5Mn34.5In16 metamagnetic shape memory alloy is investigated.
Abstract: The thermal-history-dependent (THD) isothermal magnetoresistance (MR) behavior of Ni49.5Mn34.5In16 metamagnetic shape memory alloy is investigated. Irreversibility in isothermal MR is observed in reverse martensitic transformation temperature range, while an intriguing “overshooting” phenomenon is observed in forward martensitic transformation temperature range, showing a strong thermal-history dependence of MR behavior. Such a THD MR behavior can be explained in terms of phase coexistence, THD metastable phase, and magnetic-field-induced phase transition.
TL;DR: In this paper, the spontaneous magnetization of Ni50Mn50−xInx alloys was investigated under high magnetic fields of 56 T applied with a pulsed magnet and was found to be about 6.4 and 6.0 μB/f.
Abstract: Magnetization measurements up to high magnetic fields of 56 T applied with a pulsed magnet were carried out for x = 14.0 and 15.6 in Ni50Mn50−xInx alloys. Metamagnetic behaviour from the nonmagnetic martensite phase to the ferromagnetic parent phase was observed even at x = 14.0, where no ferromagnetic phase exists in the entire temperature range under a low magnetic field. The spontaneous magnetization Is for x = 14.0 and 15.6 was deduced to be about 6.4 and 6.0 μB/f.u., respectively, and the Is increased with decreasing In concentration. This result strongly suggests that the magnetic moment of Mn atoms substituted at the In sites couples ferromagnetically to the magnetic moment of Mn atoms at the Mn sites.
TL;DR: In this article, the influence of Cu substitution for Mn on magnetization and magnetic entropy change has been investigated in Heusler alloys, Ni50Mn35−xCuxSn15 (x = 2, 5 and 10).
Abstract: The influence of Cu substitution for Mn on mag- netic properties and magnetic entropy change has been investigated in Heusler alloys, Ni50Mn35−xCuxSn15 (x = 2, 5 and 10). With increasing Cu content from x = 2 to x = 5, the martensitic transition temperature, TM , de- creases from 220 K to 120 K. Further increasing Cu up to x = 10 results in the disappearance of TM .F or samples Ni50Mn33Cu2Sn15 and Ni50Mn30Cu5Sn15, both martensitic and austenitic states exhibit ferromagnetic characteristics, but the magnetization of martensitic phase is notably lower than that of austenitic phase. The magnetization differ- ence, �M , across the martensitic transition leads to a con- siderably large Zeeman energy, μ0�M · H , which drives a field-induced metamagnetic transition. Associated with the metamagnetic behavior, a large positive magnetic en- tropy changeS takes place around TM . For the sample Ni50Mn33Cu2Sn15 ,� S reaches 13.5 J/kg·K under a mag- netic field change from 0 to 5 T.
TL;DR: In this paper, the equilibrium stress estimated from the critical stresses in stress-induced forward and reverse transformations decreased with decreasing temperature, while it became almost constant at temperatures below about 140 K. This anomaly can be explained by the abnormal temperature dependence of the transformation entropy change, which has also been detected by magnetization measurement.
Abstract: Stress-induced martensitic transformation below room temperature for a Ni45Co5Mn36.1In13.9 single-crystal, in which no martensitic transformation occurs during cooling down to 4.2 K under zero stress, was investigated by using compression test. The equilibrium stress estimated from the critical stresses in stress-induced forward and reverse transformations decreased with decreasing temperature, while it became almost constant at temperatures below about 140 K. This anomaly can be explained by the abnormal temperature dependence of the transformation entropy change, which has also been detected by magnetization measurement.
TL;DR: Modulation of the linking groups in the Mn Schiff bases affects the interchain contacts, causing alteration of the magnetic behaviors from metamagnetism to slow magnetic relaxation, resulting in the formation of two antiferromagnetic and ferromagnetic chains.
Abstract: The reaction of [W(CN)6(bpy)]− with the corresponding Mn Schiff bases led to the formation of two antiferromagnetic (1) and ferromagnetic (2) chains. The formation of the conglomerate (2) is associated with chiral induction by the enantiomeric chelate-ring conformation of the Mn Schiff base. Modulation of the linking groups in the Mn Schiff bases affects the interchain contacts, causing alteration of the magnetic behaviors from metamagnetism (1) to slow magnetic relaxation (2).
TL;DR: In this article, a series of Ni 44−x Co x Mn 45 Sn (n = 0, 1, and 2) FSMAs were prepared by arc melting method and the peak values of magnetic entropy changes were 10.1, 14.1 and 6.2
TL;DR: In this article, the Ginzburg-Landau free energy is constructed by coupling the charge-nematic, spin-nemic and ferromagnetic order parameters together, which shows that nematic electron states can be induced by metamagnetism, and the connection between this mechanism to the anisotropic metamagnetic electron states observed in Sr$_3$Ru$_2$O$_7$ at high magnetic fields is studied in a multi-band Hubbard model with the hybridized quasi-one dimensional $d_{xz}$ and $d
Abstract: We extend the study of the Fermi surface instability of the Pomeranchuk type into systems with orbital band structures, which are common features in transition metal oxides. Band hybridization significantly shifts the spectra weight of the Landau interactions from the conventional s-wave channel to unconventional non-s-wave channels, which results in anisotropic (nematic) Fermi surface distortions even with ordinary interactions in solids. The Ginzburg-Landau free energy is constructed by coupling the charge-nematic, spin-nematic and ferromagnetic order parameters together, which shows that nematic electron states can be induced by metamagnetism. The connection between this mechanism to the anisotropic metamagnetc states observed in Sr$_3$Ru$_2$O$_7$ at high magnetic fields is studied in a multi-band Hubbard model with the hybridized quasi-one dimensional $d_{xz}$ and $d_{yz}$-bands.
TL;DR: In this article, the Ginzburg-Landau free energy is constructed by coupling the charge-nematic, spin-nemic, and ferromagnetic order parameters together, which shows that nematic electron states can be induced by metamagnetism.
Abstract: We extend the study of the Fermi surface instability of the Pomeranchuk type into systems with orbital band structures, which are common features in transition metal oxides. Band hybridization significantly shifts the spectral weight of the Landau interactions from the conventional $s$-wave channel to unconventional non-$s$-wave channels, which results in anisotropic (nematic) Fermi surface distortions even with ordinary interactions in solids. The Ginzburg-Landau free energy is constructed by coupling the charge-nematic, spin-nematic, and ferromagnetic order parameters together, which shows that nematic electron states can be induced by metamagnetism. The connection between this mechanism and the anisotropic metamagnetc states observed in ${\text{Sr}}_{3}{\text{Ru}}_{2}{\text{O}}_{7}$ at high magnetic fields is studied in a multiband Hubbard model with the hybridized quasi-one-dimensional ${d}_{xz}$ and ${d}_{yz}$ bands.
TL;DR: In this paper, the magnetic properties and magnetic entropy change ΔS have been investigated in Heusler alloys Ni51Mn49−xInx (x=15.6, 16.0, and 16.2).
Abstract: Magnetic properties and magnetic entropy change ΔS have been investigated in Heusler alloys Ni51Mn49−xInx (x=15.6, 16.0, and 16.2). By tuning Ni, Mn, and In contents around composition Ni50Mn34In16, large ΔS with small thermal hysteresis near room temperature can be achieved. Martensitic temperature Tm shifts from 308 K to 253 K with x varying from 15.6 to 16.2. The thermal hysteresis around Tm is small, <2 K, for all samples. Because of the fundamental difference in magnetization around Tm, an external magnetic field induces a metamagnetic transition from the martensitic to the austenitic state. As a result, a large magnetic entropy change with positive sign appears in a wide temperature range. The size of ΔS reaches 19, 20, and 33 J/kg K under 5 T magnetic field at 253, 262, and 308 K for samples x=15.6, 16.0, and 16.2, respectively.
TL;DR: The influence of interstitial hydrogen on the electronic structure and the itinerant-electron metamagnetic transition in strong magnetocaloric compound La(Fe 0.88 Si 0.12 ) 13 H 1.6 has been investigated by Mossbauer spectroscopy.
TL;DR: A large spontaneous strain with the value of about 0.12% upon martensitic transformation has been observed in this alloy, which is almost three times larger than that in ternary Ni 46Cu4Mn38Sn12 Heusler alloy.
Abstract: Spontaneous strains during martensitic transformation and magnetic-field-induced transformation have been systemically studied for Ni46Cu4Mn38Sn12 Heusler alloy, respectively. A large spontaneous strain with the value of about 0.12% upon martensitic transformation has been observed in this alloy, which is almost three times larger than that in ternary Ni–Mn–Sn alloy. In addition, such a value of strain can be obtained through a fully reverse martensitic transformation induced by a field of about 45 kOe, exhibiting a considerable metamagnetic shape memory effect without any prestrain. This behavior can be attributed to magnetoelastic coupling between stable martensite and metastable fraction of austenite.
TL;DR: In this paper, hydrogen insertion into Ni51Mn49−xInx (x=16.2,16.6) Heusler alloys was described and the interstitial compounds were fabricated.
Abstract: By hydrogen insertion into Ni51Mn49−xInx (x=16.2,16.6) Heusler alloys, the interstitial compounds Ni51Mn49−xInxHδ were fabricated. The introduction of H atoms does not change the L21 structure of the alloys but shifts martensitic temperature (TM) to lower temperature. Magnetic measurements indicated the hydrogenated Ni51Mn49−xInxHδ compounds retain the metamagnetic properties although the ferromagnetic behavior of martensitic phases is slightly enhanced due to the introduction of H atoms. The strong metamagnetic behaviors result in large magnetocaloric effect (MCE). By controlling H content an extended temperature range having large MCE can be achieved.
TL;DR: It is shown that a Stoner model with electronic band dispersion can reproduce this phase diagram and transport behavior and it is proposed that this is a magnetic analogue of the spatially inhomogeneous superconducting Fulde-Ferrel-Larkin-Ovchinnikov state.
Abstract: The phase diagram of ${\mathrm{Sr}}_{3}{\mathrm{Ru}}_{2}{\mathrm{O}}_{7}$ contains a metamagnetic transition that bifurcates to enclose an anomalous phase with intriguing properties---a large resistivity with anisotropy that breaks the crystal-lattice symmetry. We propose that this is a magnetic analogue of the spatially inhomogeneous superconducting Fulde-Ferrel-Larkin-Ovchinnikov state. We show---through a Ginzburg-Landau expansion where the magnetization transverse to the applied field can become spatially inhomogeneous---that a Stoner model with electronic band dispersion can reproduce this phase diagram and transport behavior.
TL;DR: In this paper, a phenomenological rationalization for the field dependence and metamagnetism crossover of the system is provided, demonstrating the importance of both spin-phonon coupling and a small field-dependent easy-axis anisotropy in accurately describing the magnetization process of CuFeO2.
Abstract: Pulsed-field magnetization experiments extend the typical metamagnetic staircase of CuFeO2 up to 58 T to reveal an additional first-order phase transition at high field for both the parallel and perpendicular field configuration. Virtually complete isotropic behavior is retrieved only above this transition, indicating the high-field recovery of the undistorted triangular lattice. A consistent phenomenological rationalization for the field dependence and metamagnetism crossover of the system is provided, demonstrating the importance of both spin-phonon coupling and a small field-dependent easy-axis anisotropy in accurately describing the magnetization process of CuFeO2.
TL;DR: In this article, a simple Landau model was used to calculate magnetization isotherms considering magnetic hysteresis, and the model parameters were chosen to fit the magnetic and magnetocaloric data of MnAs compound.
Abstract: We have explored a simple Landau model to calculate magnetization isotherms considering magnetic hysteresis. The model parameters have been chosen to fit the magnetic and magnetocaloric data of MnAs compound. Experimental data show that there is a great difference between the isothermal variation of the entropy (ST) obtained from isotherms measured increasing and decreasing magnetic field. This great difference is reproduced theoretically. From the experimental and phenomenological isotherms, we calculated the ST. From the theoretical entropy, we also obtained ST, which does not present the colossal peak.
01 Jan 2009
TL;DR: A second pocket of superconductivity is discovered at higher fields applied close to the b-axis, enveloping a sudden magnetic moment rotation transition at H(R) = 12 T and the possibility that magnetic fluctuations emerging from a quantum critical point provide the pairing mechanism for super conductivity is discussed.
Abstract: As ferromagnetism and superconductivity are usually considered to be antagonistic, the discovery of their coexistence in UGe 2 , URhGe, UIr and UCoGe has attracted a lot of interest. The mechanism to explain such a state has, however, not yet been fully elucidated. In these compounds superconductivity may be unconventional: Cooper pairs could be formed by electrons with parallel spins and magnetic fluctuations might be involved in the pairing mechanism. URhGe becomes ferromagnetic below a Curie temperature of 9.5 K, with a spontaneous moment aligned to the c-axis. For temperatures below 260 mK and fields lower than 2 T, superconductivity was first observed in 2001. Recently, we discovered a second pocket of superconductivity. This new pocket of superconductivity appears at higher fields applied close to the b-axis, enveloping a sudden magnetic moment rotation transition at H R = 12 T. Detailed studies of the field induced metamagnetic transition and superconductivity are presented. The possibility that magnetic fluctuations emerging from a quantum critical point provide the pairing mechanism for superconductivity is discussed.
TL;DR: In this article, the magnetic entropy, hysteresis loss and refrigerant capacity of NaZn 13 -type La 0.7 Pr 0.3 Fe 13− x Si x (1.5⩽ x ⩽2.0) compounds have been investigated.