Showing papers on "Metamagnetism published in 2004"
TL;DR: Experimental evidence is presented for the formation of a nonsuperconducting phase in the vicinity of a magnetic field–tuned quantum critical point in ultrapure crystals of the ruthenate metal Sr3Ru2O7, and the possibility that the observed phase is due to a spin-dependent symmetry-breaking Fermi surface distortion is discussed.
Abstract: Condensed systems of strongly interacting electrons are ideal for the study of quantum complexity. It has become possible to promote the formation of new quantum phases by explicitly tuning systems toward special low-temperature quantum critical points. So far, the clearest examples have been appearances of superconductivity near pressure-tuned antiferromagnetic quantum critical points. We present experimental evidence for the formation of a nonsuperconducting phase in the vicinity of a magnetic field-tuned quantum critical point in ultrapure crystals of the ruthenate metal Sr3Ru2O7, and we discuss the possibility that the observed phase is due to a spin-dependent symmetry-breaking Fermi surface distortion.
198 citations
TL;DR: In this paper, the thermal conductivity and diffusivity of La(Fe0.88Si0.12)13H1.0 have been investigated, together with those of other candidates for magnetic refrigerants working in the vicinity of room temperature such as Gd, Gd5Si2Ge2 and MnAs.
Abstract: La(FexSi1−x)13 and their hydrides exhibit large magnetocaloric effects due to the itinerant-electron metamagnetic transitions in a wide temperature range covering room temperature. Thermal conductivity and diffusivity of La(Fe0.88Si0.12)13 and La(Fe0.88Si0.12)13H1.0 have been investigated, together with those of other candidates for magnetic refrigerants working in the vicinity of room temperature such as Gd, Gd5Si2Ge2 and MnAs. The thermal conductivity in the vicinity of room temperature for La(Fe0.88Si0.12)13H1.0 is larger than that for Gd5Si2Ge2 and MnAs, and almost identical to that for Gd. Furthermore, the thermal diffusivity in the vicinity of room temperature for La(Fe0.88Si0.12)13H1.0 is as large as that for Gd and Gd5Si2Ge2, and larger than that for MnAs. Consequently, La(FexSi1−x)13 and their hydrides are promising as the magnetic refrigerants from the standpoint of thermal transport properties.
128 citations
TL;DR: Two new cobalt phosphates, synthesized by hydrothermal methods in the presence of aromatic amines, and characterized by single-crystal X-ray diffraction and magnetic susceptibility, show long-range antiferromagnetic ordering below 15 K and metamagnetic behaviors.
Abstract: Two new cobalt phosphates, [Co(3)(pyz)(HPO(4))(2)F(2)] (1) and [Co(3)(4,4'-bpy)(HPO(4))(2)F(2)].xH(2)O (x approximately 0.7) (2), have been synthesized by hydrothermal methods in the presence of aromatic amines, and characterized by single-crystal X-ray diffraction and magnetic susceptibility. Their structures consist of neutral sheets of fluorinated cobalt phosphate which are pillared through pyrazine and 4,4'-bipyridine molecules to form 3D frameworks. The structures are related to that of the mineral lazulite. Both compounds show long-range antiferromagnetic ordering below 15 K and metamagnetic behaviors. Compound 1 reveals a two-step magnetic phase transition. Crystal data for 1: monoclinic, space group C2/c (No. 15), a = 21.809(4) A, b = 7.370(1) A, c = 7.395(1) A, beta = 103.753(3) degrees, and Z = 4. Crystal data for 2 are the same as those for 1 except a = 29.940(2) A, b = 7.4421(5) A, c = 7.4170(5) A, and beta = 93.444(1) degrees.
75 citations
TL;DR: In this article, the authors have grown RFe2Ge2 single crystals for R=Y and ten members of the lanthanide series (Pr, Nd, Sm, Gd, Tm, Lu) using Sn flux as the solvent.
72 citations
TL;DR: In this article, a strong dependence of magnetization and resistivity changes in manganites on the cooling rate was observed and it was shown that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state and subsequent magnetization jumps.
Abstract: Magnetic field induced steplike changes in magnetization and resistivity of ${\mathrm{Sm}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}\mathrm{Mn}{\mathrm{O}}_{3}$ manganites were studied. A strong dependence of these features on the cooling rate was observed. Magnetostriction, however, does not show the presence of large strain in our samples. From all these features we can rule out the conventional explanation of magnetization jumps as a consequence of martensitic transition. We propose instead that quenched by fast cooling disorder leads to the formation of an inhomogeneous metastable state and to subsequent magnetization jumps.
71 citations
TL;DR: In this paper, a theoretical analysis of the magnetization reversal process in a bi-layer structure with hard and soft (with metamagnetic transition) magnetic layers on an example of an $\mathrm{Fe}Mathrm{Pt}∕\mathrm {Fe}mathrm
Abstract: We present a theoretical analysis of the magnetization reversal process in a bi-layer structure with hard and soft (with metamagnetic transition) magnetic layers on an example of an $\mathrm{Fe}\mathrm{Pt}∕\mathrm{Fe}\mathrm{Rh}$ bi-layer. The latter leads to the formation of a new type of exchange spring which results in a significant reduction of the switching field in the temperature range of the metamagnetic (from antiferromagnetic to ferromagnetic state) transition in an FeRh layer. Analytic expressions for nucleation and switching fields are presented along with results of numerical micromagnetic simulations. The reduction of the switching field due to the metamagnetic transition is controlled by the following microscopic parameters: (i) the interfacial exchange coupling parameter ${J}_{12}$; (ii) saturation magnetization of the FeRh layer in a ferromagnetic phase; (iii) the metamagnetic transition temperature. The switching field dependence on the ${J}_{12}$ parameter is shown to saturate quickly as it approaches the bulk exchange interaction value which has been evaluated using first-principles method used also to verify the electronic nature of the metamagnetic transition. Theoretical results are discussed in the context of recent experimental observations.
65 citations
TL;DR: In this article, the temperature dependence of the Landau coefficients has been derived by fitting the magnetization, M ( μ 0 H ), using the landau expansion of the magnetic free energy.
65 citations
TL;DR: In this paper, the magnetic properties of four compounds in the series YBaCo4?xZnxO7 (x = 0, 1, 2, 3) were investigated.
Abstract: The magnetic properties of four compounds in the series YBaCo4?xZnxO7 (x = 0, 1, 2, 3) were investigated.?For all compositions magnetic transitions were observed (Tf) over the temperature range 66?3?K observed with ac susceptibility and dc magnetometry. Futhermore, all ac measurements proved to be frequency-dependent:?Tf increases with an increase in frequency. The real part of the magnetic susceptibility (?') was, in all four cases, accompanied by an energy loss in the magnetic coupling, indicated as contributions to the imaginary part (?''). The maximum ?'' appeared just below the maximum ?'. Using the Arrhenius law, the Vogel?Fulcher law and the power law, it was possible to conclude that the compounds should be defined as spin-glass-like materials. The dc magnetizations clearly show differences between field-cooled and zero-field-cooled measurements. None of the compounds exhibited any metamagnetic property and, using a new data analysis method, a possible saturation field could be calculated for YBaCo4O7. Relaxation measurements on YBaCo3ZnO7 indicate that the system has no ageing effects. The magnetic properties can be described as having two connected magnetic substructures represented as dimensionalities:?axial (1D) and in-plane (2D). This was concluded by comparing the magnetic properties with structural details.
62 citations
TL;DR: Measurements on ultraclean single crystals of the bilayered ruthenate metal Sr3Ru2O7, which has a magnetic-field-tuned quantum critical point, show strong enhancement of the resistivity in a narrow field window and the region of anomalous behavior is bounded at low temperatures by two first-order phase transitions.
Abstract: We present measurements on ultraclean single crystals of the bilayered ruthenate metal ${\mathrm{Sr}}_{3}{\mathrm{Ru}}_{2}{\mathrm{O}}_{7}$, which has a magnetic-field-tuned quantum critical point. Quantum oscillations of differing frequencies can be seen in the resistivity both below and above its metamagnetic transition. This frequency shift corresponds to a small change in the Fermi surface volume that is qualitatively consistent with the small moment change in the magnetization across the metamagnetic transition. Very near the metamagnetic field, unusual behavior is seen. There is a strong enhancement of the resistivity in a narrow field window, with a minimum in the resistivity as a function of temperature below 1 K that becomes more pronounced as the disorder level decreases. The region of anomalous behavior is bounded at low temperatures by two first-order phase transitions. The implications of the results are discussed.
60 citations
TL;DR: In this article, a giant magnetoresistance effect in the Mn(1.82)Vo(0.18)Sb compound is reported, which is associated with a first-order metamagnetic transition from an antiferromagnetic to a ferrimagnetic state, induced by an external field.
58 citations
TL;DR: In this paper, powder X-ray diffraction data confirmed the hexagonal AlNiZr-type structure (P 6 2 ǫm space group), an ordered variant of the Fe2P structure type.
TL;DR: In this article, the authors show that the low-temperature behavior of the n-layer ruthenates Srn + 1RunO3n+1 can be understood as a result of a Van Hove singularity (VHS).
Abstract: The problem of quantum criticality in the context of itinerant ferro- or metamagnetism has received considerable attention (Grigera S. A. et al., Science 294 (2001) 329; Pfleiderer C. et al., Nature 414 (2001) 427). It has been proposed that a new kind of quantum criticality is realised in materials such as MnSi or Sr3Ru2O7. We show, based on a mean-field theory, that the low-temperature behaviour of the n-layer ruthenates Srn + 1RunO3n + 1 can be understood as a result of a Van Hove singularity (VHS). We consider a single band whose Fermi energy, EF, is close to the VHS and deduce a complex phase diagram for the magnetism as a function of temperature, magnetic field and EF. The location of EF with respect to the VHS depends on the number of layers or can be tuned by pressure. We find that the ferromagnetic quantum phase transition in this case is not of second but of first order, with a metamagnetic quantum critical end-point at high magnetic field. Despite its simplicity, this model describes well the properties of the uniform magnetism in the single-, double- and triple-layer ruthenates. We would like to emphasise that the origin of this behaviour lies in the band structure.
TL;DR: In this article, the magnetization, specific heat, and transport measurements of a high quality Na0.85CoO2 single crystal in applied magnetic fields up to 14 T were reported.
Abstract: We report the magnetization, specific heat, and transport measurements of a high quality Na0.85CoO2 single crystal in applied magnetic fields up to 14 T. At high temperatures, the system is in a paramagnetic phase. It undergoes a magnetic phase transition below similar to20 K. For the field H parallel to c, the measurement data of magnetization, specific heat, and magnetoresistance reveal a metamagnetic transition from an antiferromagnetic state to a quasiferromagnetic state at about 8 T at low temperatures. However, no transition is observed in the magnetization measurements up to 14 T for H perpendicular to c. The low temperature magnetic phase diagram of Na0.85CoO2 is determined.
TL;DR: In this article, the authors show that the low-temperature behavior of the n-layer ruthenates can be understood as a result of a Van Hove singularity (VHS).
Abstract: The problem of quantum criticality in the context of itinerant ferro- or metamagnetism has received considerable attention [S. A. Grigera et. al., Science 294, 329 (2001); C. Pfleiderer et. al., Nature, 414, 427 (2001)]. It has been proposed that a new kind of quantum criticality is realised in materials such as MnSi or Sr_3Ru_2O_7. We show based on a mean-field theory that the low-temperature behaviour of the n-layer ruthenates Sr_{n+1}Ru_nO_{3n+1} can be understood as a result of a Van Hove singularity (VHS). We consider a single band whose Fermi energy, E_F, is close to the VHS and deduce a complex phase diagram for the magnetism as a function of temperature, magnetic field and E_F. The location of E_F with respect to the VHS depends on the number of layers or can be tuned by pressure. We find that the ferromagnetic quantum phase transition in this case is not of second but of first order, with a metamagnetic quantum critical endpoint at high magnetic field. Despite its simplicity this model describes well the properties of the uniform magnetism in the single, double and triple layer ruthenates. We would like to emphasise that the origin of this behaviour lies in the band structure.
TL;DR: FeIII(OH) is the first carboxylate with a 3D open structure that has been synthesized up to now as discussed by the authors, and its structure is built up from chains of octahedra connected by carboxyclic ligands.
TL;DR: Magnetocaloric effects (MCEs) caused by the itinerant-electron metamagnetic transition for the La(FexSi1−x)13 compounds and their hydrides have been investigated by the direct measurement as discussed by the authors.
TL;DR: In this article, the magnetization behavior across a metamagnetic transition from an antiferromagnetic state to a ferrimagnetic state is investigated in detail for compound (mn, n, 2, sb, sn, 0.95, n).
Abstract: Magnetization behavior across a metamagnetic transition from an antiferromagnetic state to a ferrimagnetic state is investigated in detail for compound ${\mathrm{Mn}}_{2}{\mathrm{Sb}}_{0.95}{\mathrm{Sn}}_{0.05}$. The study clearly brings out various generic features associated with a first-order transition, viz., the appearance of hysteresis and the coexistence of magnetic phases. We also observe that the magnetization versus field butterfly loops occurs, while the virgin curve lies outside the envelope magnetization curve. The electronic specific-heat coefficient at low temperatures increases with increasing applied magnetic field, after the field is larger than the critical transition field. This is direct evidence of the formation of a super-zone gap that yields the change of density of electric states and further proves that the large magnetoresistance effect in intermetallic compounds is originated from the reconstruction of Fermi surface due to the collapse of the super-zone gap after the metamagnetic transition.
TL;DR: In this paper, the authors investigated the origin of the huge magnetocaloric effect in a manganite system with ferro-antiferromagnetic phase mixture at low temperatures and carried out magnetic measurements in fields up to 100 kOe in order to show that both a high hysteretic behavior and a metamagnetic transition in the antiferrome state are responsible for the large magnetic entropy change.
Abstract: We have investigated the origin of the huge magnetocaloric effect in a manganite system with ferro–antiferromagnetic phase mixture at low temperatures. We carried out magnetic measurements in fields up to 100 kOe in order to show that both a high hysteretic behavior and a metamagnetic transition in the antiferromagnetic state are responsible for the large magnetic entropy change. The temperature where the maximum of the magnetic entropy change occurs can be tuned by varying the maximum value of the applied magnetic field to the system. This last procedure can open a new perspective for charge-ordered manganite applications to magnetic refrigeration at low temperatures.
TL;DR: In this article, the authors investigated the process of a metamagnetic transition between the ferromagnetic and paramagnetic states in the LaFe11.7Si1.3 compound, which has both magnetocaloric and large magnetovolume effects.
Abstract: We have investigated the process of a metamagnetic transition (MT) between the ferromagnetic and paramagnetic states in the LaFe11.7Si1.3 compound, which has both giant magnetocaloric and large magnetovolume effects. The nucleation in MT, which indicates the coexistence of two phases, can be obviously activated by thermal fluctuation in the presence of magnetic fields. The experimental magnetization curves are well reproduced based on the itinerant metamagnetism theory considering thermal activation, and are largely different from the athermal MT. The critical nucleation volume for the phase transition approximates to 300 nm(3), and the surface energy to prevent MT is about 2x10(-4) J/m(2).
TL;DR: Mn2Sb is a ferrimagnet, and substitution of Co or Cr for Mn above the critical concentration results in the appearance of a spontaneous first-order magnetic phase transition from ferrimagnetic (FRI) to antiferromagnetic (AF) with decreasing temperature below Tt.
Abstract: Mn2Sb is a ferrimagnet, and substitution of Co or Cr for Mn above the critical concentration results in the appearance of a spontaneous first-order magnetic phase transition from ferrimagnetic (FRI) to antiferromagnetic (AF) with decreasing temperature below Tt . At T
TL;DR: In this article, the quasi-elastic excitation in the vicinity of the reciprocal lattice point (110) with an energy of 4 meV is significantly enhanced at T =04 K, indicating that the metamagnetic crossover in this compound is associated with a field-induced ferromagnetic correlation.
Abstract: Neutron inelastic scattering experiments have been performed on the paramagnetic heavy fermion compound CeRu 2 Si 2 in magnetic field along the crystal c -axis Around the metamagnetic crossover field H m =77 T, the quasi-elastic excitation in the vicinity of the reciprocal lattice point (110) with an energy of 04 meV is significantly enhanced at T =04 K The result indicates that the metamagnetic crossover in this compound is associated with a field-induced ferromagnetic correlation The observation is consistent with the recent theoretical prediction by Satoh and Ohkawa based on quasi-particle band spectrum considerations
TL;DR: In this article, a new mechanism of magnetoresistivity in itinerant metamagnets with a structural disorder is introduced based on analysis of experimental results on magnetorestivity, susceptibility, and magnetization of structurally disordered alloys.
Abstract: New mechanism of magnetoresistivity in itinerant metamagnets with a structural disorder is introduced basing on analysis of experimental results on magnetoresistivity, susceptibility, and magnetization of structurally disordered alloys $({\mathrm{Y}}_{1\ensuremath{-}x}{\mathrm{Gd}}_{x}){\mathrm{Co}}_{2}.$ In this series, ${\mathrm{YCo}}_{2}$ is an enhanced Pauli paramagnet, whereas ${\mathrm{GdCo}}_{2}$ is a ferrimagnet ${(T}_{\mathrm{c}}=400\mathrm{K})$ with Gd sublattice coupled antiferromagnetically to the itinerant $\mathrm{Co}\ensuremath{-}3d$ electrons. The alloys are paramagnetic for $xl0.12.$ Large positive magnetoresistivity has been observed in the alloys with magnetic ground state at temperatures $Tl{T}_{\mathrm{c}}.$ We show that this unusual feature is linked to a combination of structural disorder and metamagnetic instability of itinerant $\mathrm{Co}\ensuremath{-}3d$ electrons. This new mechanism of the magnetoresistivity is common for a broad class of materials featuring a static magnetic disorder and itinerant metamagnetism.
TL;DR: The strongly exchange enhanced Pauli paramagnet LaCo was found to exhibit an itinerant metamagnetic phase transition with indications for quantum criticality as discussed by the authors, which is the lowest value ever found for rare earth intermetallic compounds.
Abstract: The strongly exchange enhanced Pauli paramagnet LaCo$_9$Si$_4$ is found to exhibit an itinerant metamagnetic phase transition with indications for metamagnetic quantum criticality. Our investigation comprises magnetic, specific heat, and NMR measurements as well as ab-initio electronic structure calculations. The critical field is about 3.5 T for $H||c$ and 6 T for $H\bot c$, which is the lowest value ever found for rare earth intermetallic compounds. In the ferromagnetic state there appears a moment of about 0.2 $\mu_B$/Co at the $16k$ Co-sites, but sigificantly smaller moments at the 4d and $16l$ Co-sites.
TL;DR: The magnetic and magnetocaloric properties of Er(Co1−x6)2 compounds with 0⩽x0.075 have been studied to determine their suitability as magnetic refrigerant materials as discussed by the authors.
Abstract: The magnetic and magnetocaloric properties of Er(Co1−xSix)2 compounds with 0⩽x⩽0.075 have been studied to determine their suitability as magnetic refrigerant materials. The strength of itinerant electron metamagnetism was found to decrease with Si concentration, which is responsible for the reduction of the magnetocaloric effect. Magnetization curves at low temperatures show the existence of a critical field for magnetization to increase, which is a consequence of domain wall pinning. The critical field and the coercive field were found to increase with Si concentration.
TL;DR: The magnetization of MnSi has been measured at low temperatures down to 14 K under high pressures up to P=17 GPa and magnetic fields up to B=9 T.
TL;DR: In this article, the temperature dependence of the paramagnetic susceptibility χ m (T ) taken in 2500-Oe, the resistivity ρ (T ), and the thermoelectric power α ( T ) of DyBaCo 2 O 5+ x, which has Ba and Dy ordered into alternate (001) planes of an oxygen-deficient perovskite, have revealed a phase segregation in the compositional range 0.3⩽ x 2 O 0.51 (1.51) planes.
Journal Article•
TL;DR: In this paper, strongly exchange enhanced Pauli paramagnet LaCo 9 Si 4 (Si 4) was found to exhibit an itinerant metamagnetic phase transition with indications for quantum criticality.
Abstract: The strongly exchange enhanced Pauli paramagnet LaCo 9 Si 4 is found to exhibit an itinerant metamagnetic phase transition with indications for metamagnetic quantum criticality. Our investigation comprises magnetic, specific heat, and nuclear magnetic resonance measurements as well as ab initio electronic structure calculations. The critical field is about 3.5 T for H∥c and 6 T for H⊥c, which is the lowest value ever found for rare earth intermetallic compounds. In the ferromagnetic state there appears a moment of about 0.2 μ B /Co at the 16k Co-sites, but significantly smaller moments at the 4d and 16l Co-sites.
TL;DR: In this article, a magnetic susceptibility study on mineral crystal atacamite Cu2Cl(OH)3 showed that the crystal is an intrinsic antiferromagnet with T N = 9 K.
TL;DR: In this paper, a cascade of metamagnetic phase transitions with unusually broad regions of metastable phase-coexistence and specific multidomain structures are characterized by a new class of magnetic materials with unique magnetic properties.