High-field Phase Diagram Research Articles

Anisotropic magnetic and quadrupolar H−T phase diagram of CeRh2As2

The tetragonal heavy-fermion compound CeRh2As2 has intriguing low-temperature symmetry-breaking phases whose nature is unclear. The unconventional superconducting phase is complemented by other normal-state phases which presumably involve ordering of 4f electron multipoles supported by the Kramers doublets split by the tetragonal crystal electric field (CEF). The most striking aspect is the pronounced anisotropic H−T phase boundary for in-plane and out-of plane field directions. Using a localized 4f CEF model we demonstrate that its essential features can be understood as the result of competing low-field easy-plane magnetic order and field-induced quadrupolar order of xy type. We present calculations based on coupled multipole random phase approximation response function approach as well as molecular field treatment in the ordered regime. We use an analytical approach for a reduced quasiquartet model and numerical calculations for the complete CEF level scheme. We discuss the quantum critical properties as function of multipolar control parameters and explain the origin of a pronounced ac anisotropy of the H−T phase diagram. Finally, the field and temperature evolution of multipolar order parameters is derived and the high-field phase diagram is predicted. Published by the American Physical Society 2024

Effects of Bi3+ doping on the charge ordering and high-field phase diagram of La0.5-xBixCa0.5MnO3

La0.5-xBixCa0.5MnO3 (x = 0, 0.05, 0.1 and 0.2) compounds have been prepared to study the effects of Bi3+ substitution on the structure, magnetic and magnetotransport properties. Experimental results show that Bi3+ dopants have induced a distinct lattice distortion and phase separated state in which the long range ferromagnetic order turns into short range ferromagnetic clusters, and the charge ordering/antiferromagnetism and ferromagnetic clusters coexist in the system. Bi3+ doping induced disorders lead to the presence of a Griffith-like phase. The hybridization between Bi3+-6s orbitals and O2–-2p orbitals produces a localization of O2–-2p electrons and lattice distortion, which plays an important role in favoring charge ordering state and multiple magnetic ordering. The charge ordering antiferromagnetic collapses into ferromagnetic phase through a metamagnetic transition with applying a sufficiently high magnetic field. A T-HC phase diagram was determined based on the magnetization and electrical transport measurements, in which the phase boundary is figured out.

Evolution of magnetic field induced ordering in the layered quantum Heisenberg triangular-lattice antiferromagnet Ba3CoSb2O9

Quantum fluctuations in the effective spin one-half layered structure triangular-lattice quantum Heisenberg antiferromagnet Ba$_3$CoSb$_2$O$_9$ lift the classical degeneracy of the antiferromagnetic ground state in magnetic field, producing a series of novel spin structures for magnetic fields applied within the crystallographic ab plane. Theoretically unresolved, however, are the effects of interlayer antferromagnetic coupling and transverse magnetic fields on the ground states of this system. To address these issues, we have used specific heat, neutron diffraction, thermal conductivity, and magnetic torque measurements to map out the phase diagram as a function of magnetic field intensity and orientation relative to the crystallographic ab plane. For H parallel to the ab plane, we have discovered an additional, previously unreported magnetic-field-induced phase transition at low temperature and an unexpected tetracritical point in the high field phase diagram, which - coupled with the apparent second-order nature of the phase transitions - eliminates several theoretically proposed spin structures for the high field phases. Our calorimetric measurements as a function of magnetic field orientation are in general agreement with theory for field-orientation angles close to plane parallel but diverge at angles near plane perpendicular; a predicted convergence of two phase boundaries at finite angle and a corresponding change in the order of the field induced phase transition is not observed experimentally. Our results emphasize the role of interlayer coupling in selecting and stabilizing field-induced phases, provide new guidance into the nature of the magnetic order in each phase, and reveal the need for new physics to account for the nature of magnetic ordering in this archetypal 2D spin one-half triangular lattice quantum Heisenberg antiferromagnet.

High-field phase diagram of Ni3V2O8 studied by specific heat and magnetocaloric effect measurements

The H–T phase diagram of Ni3V2O8 is very rich and remains puzzling in a high magnetic field range. Through the state-of-the-art specific heat measurement in pulsed high field to 35 T and magnetocaloric effect measurement up to 45 T, we successfully construct the high-field phase diagram of Ni3V2O8 for fields applied along the b axis. The phase boundaries are corrected for previous results by magnetization and magneto-optical measurements. The resulting phase diagram shows that the high temperature incommensurate (HTI) phase develops well to high fields and low temperatures. In addition to the early reported C′, C, low temperature incommensurate (LTI) and HTI phases, we explore a new magnetic ordered phase called HF1 in fields of 10–30 T. A multicritical point is also observed at 6 K and 8 T. Furthermore, the specific heat data reveal enhancements of the anomalies at ∼4 K, probably associated with a strong spin–lattice coupling in this frustrated multiferroic material.

High-field phase transitions in the orbitally ordered multiferroic GeV4S8

The high-field (H,T) phase diagram of the multiferroic lacunar spinel $\mathrm{Ge}{\mathrm{V}}_{4}{\mathrm{S}}_{8}$ has been studied by ultrasound, magnetization, and pyrocurrent experiments in magnetic fields up to 60 T. The title compound consists of molecular building blocks, with vanadium ${\mathrm{V}}_{4}$ clusters characterized by a unique electron density. These vanadium tetrahedra constitute a Jahn-Teller active entity, which drive an orbital-ordering transition at 30 K with the concomitant appearance of ferroelectricity. Ultrasound and magnetization experiments reveal sharp anomalies in magnetic fields of 46 T, which are associated with a first-order phase transition into an orbitally disordered state characterized by significant field and temperature hystereses. We report a sequence of complex magnetic, polar, and orbitally ordered states, i.e., the appearance of two orbitally ordered phases OO1 and OO2 for ${\ensuremath{\mu}}_{0}H<45\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ and $T<30\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. Beyond the paraelectric phase we further evidenced three ferroelectric phases, FE1, FE2, and FE3. Finally, antiferromagnetic (AFM) order $(T<15\text{ K})$ and fully polarized ferromagnetic order $({\ensuremath{\mu}}_{0}H>60\phantom{\rule{0.16em}{0ex}}\mathrm{T})$ have been observed in $\mathrm{Ge}{\mathrm{V}}_{4}{\mathrm{S}}_{8}$. At low temperatures and for fields below 40 T, AFM order coexists with the polar phase FE3 identifying a multiferroic state. Our results demonstrate a fascinating competition of the different orders, which the material manifests in high magnetic fields and at low temperatures.

High-field magnetization and magnetic phase diagram of metamagnetic shape memory alloys Ni50−xCoxMn31.5Ga18.5 ( x = 9 and 9.7)

Magnetic phase diagrams of the metamagnetic shape memory alloys Ni50-xCoxMn31.5Ga18.5 (x = 9 and 9.7) were produced from high-field magnetization measurements up to 56 T. For both compounds, magnetic field induced martensitic transformations are observed at various temperatures below 300 K. Hysteresis of the field-induced transformation shows unconventional temperature dependence: it decreases with decreasing temperature after showing a peak. Magnetic susceptibility measurement, microscopy, and X-ray diffraction data suggest a model incorporating the magnetic anisotropy and Zeeman energy in two variants, which qualitatively explains the thermal and the magnetic field history dependence of the hysteresis in these alloys.

Effects of Bi3+ doping on charge ordering and high magnetic field phase diagram of Nd0.6-xBixCa0.4MnO3

We report the doping effects and pulsed high magnetic field-induced charge ordering to ferromagnetic phase transitions in manganites Nd0.6-xBixCa0.4MnO3 (0 ≤ x ≤ 0.4). The experimental results reveal that the charge ordering is significantly enhanced upon Bi3+ doping, and the charge ordering temperature increases with increasing Bi3+ content. With applying pulsed high magnetic field, the charge ordering phase collapses into ferromagnetic phase through a metamagnetic transition. The phase diagram of Nd0.6-xBixCa0.4MnO3 has been determined by the high magnetic field studies, in which the charge ordering and ferromagnetic phase boundary is clearly figured out. The critical fields for melting the charge ordering phase of Nd0.6-xBixCa0.4MnO3 increase significantly with increasing Bi3+ content, which is revealed to reach up to 33.5 T for the sample with x = 0.3. Based on the hybridization between Bi-6s orbitals and O-2p orbitals, we assume that the 6s2 lone-pair character of Bi3+ plays a crucial role in favoring the charge ordering in Nd0.6-xBixCa0.4MnO3 (0 ≤ x ≤ 0.4).

Magnetic behavior and complete high-field magnetic phase diagram of the orthoferrite ErFeO3

Magnetic transitions in a single crystal of the orthoferrite ${\mathrm{ErFeO}}_{3}$ have been studied between 2 and 300 K using conventional superconducting quantum interference device measurements as well as pulsed high magnetic fields of up to 58 T. Spontaneous spin reorientations, as well as temperature and magnetic field induced spin reorientations, have been observed. At spin-reorientation transition temperatures, the ${\mathrm{Fe}}^{3+}$ sublattice exhibits a ${\mathrm{\ensuremath{\Gamma}}}_{4}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Gamma}}}_{2}$ transition where the magnetic coupling between the net magnetic moment of ${\mathrm{Fe}}^{3+}$ $3d$ and ${\mathrm{Er}}^{3+}$ $4f$ is antiferromagnetic, and the temperature dependence of the magnetization suggests that the order of magnitude of the interaction is ${J}_{\text{Er-Er}}l{J}_{\text{Er-Fe}}l{J}_{\mathrm{Fe}\text{\ensuremath{-}}\mathrm{Fe}}$. However, the magnetic coupling varies widely with temperature and/or magnetic field, which indicates that the ${\mathrm{Er}}^{3+}$ sublattice moment cannot be simply explained by the partial polarization of the paramagnetic spins due to the combination of the molecular field from the net ${\mathrm{Fe}}^{3+}$ moment and external applied magnetic fields. It is found that in a sufficiently high magnetic field, the magnetic interactions between the ${\mathrm{Fe}}^{3+}$ sublattice and the ${\mathrm{Er}}^{3+}$ sublattice are destroyed. Based on the detailed magnetization measurements, the complete high-field magnetic phase diagram has been obtained, providing an important framework for future investigations into the complicated magnetic interactions and magnetoelectric couplings in rare earth orthoferrites.

Tuning of cu doping on phase transition and high-field phase diagram of Nd0.5Sr0.5Mn1−xCuxO3

Pulsed high magnetic fields up to 52T have been used in the systematic investigation of the magnetic properties of manganites Nd0.5Sr0.5Mn1−xCuxO3 (0≤x≤0.15). The Cu-doping dependent first-order metamagnetic transitions are observed below the charge ordering temperature, which is ascribed to both Cu-doping and field-induced collapse of the charge ordering with antiferromagnetic phase. Based on the magnetization and electrical transport measurements, a three-dimensional phase diagram with coordinate axis of temperature, magnetic field, and doping level has been obtained, in which the critical fields of the metamagnetic transitions increase with the increase in Cu content and decrease with increasing temperature. The experimental results confirm that Mn-site substitution with Cu destroys the Mn3+–O2−–Mn4+ bridges and weakens the double exchange interaction between Mn3+ and Mn4+ ions, which shows an obvious tuning effect on the metamagnetic transition under the external magnetic field.

Al3+ doping effects and high-field phase diagram of La0.5Sr0.5Mn1−xAlxO3

Magnetization measurements of La0.5Sr0.5Mn1−xAlxO3 (0 ⩽ x ⩽ 0.25) under pulsed high magnetic fields up to 50 T have been carried out, in which the Al3+ ions doping and magnetic field effects on the charge-ordering/antiferromagnetic to ferromagnetic phase transitions have been discussed. A triple-phase diagram with the critical field, doping level and temperature has been determined, in which the antiferromagntic and ferromagnetic phase boundaries were clearly defined. The change from long-range charge-ordered/antiferromagnetic phases to the robust short-range ones upon the Al3+-doping was observed. According to the experimental results, we assume that Al3+ ion doping at the Mn sites dilutes the Mn3+-O-Mn4+ network, weakens the double-exchange interaction and further suppresses the FM phase (metallic conduction), which leads to the critical magnetic fields destroying the antiferromagnetic order increase with the increase of the doping level.

Electron–Hole Pairing in Presence of a Strong Magnetic Field in Graphite

The collective electronic states induced by a strong magnetic field in graphite are believed to emerge because of the formation of electron–hole pairs. Researchers in Tokyo uncover new features in the high-field phase diagram and put forward a new scenario.

High magnetic field phase diagram in electron-doped manganites La(0.4)Ca(0.6)Mn(1-y)Cr(y)O3.

We report the charge-order to ferromagnetic phase transition induced by pulsed high magnetic field and impurity doping effects in manganites La0.4Ca0.6(Mn1−yCry)O3 (0 ≤ y ≤ 0.2). Significant charge-order suppression and ferromagnetic tendency upon the Cr3+-doping are evidenced, and three different ground states are identified, namely the charge-order state, the phase separated state, and the spin-glass like state. Phase diagram in the H-y plane at 4.2 K is determined by the high magnetic field study, in which the charge-order and ferromagnetic phase boundary is clearly figured out. The critical magnetic field for melting the charge-order phase of La0.4Ca0.6MnO3 is revealed to reach up to 46 T at 4.2 K. Interestingly, distinct responses of the three states to the high magnetic field are observed, indicating the special physics regarding the charge order melting process in each state. The mechanism of the doping induced charge-order suppression and ferromagnetism promotion can be understood by the competition between the antiferromagnetic interaction of Cr-Mn and local enhancement of electron hopping by Cr3+.

High-field magnetic phase diagram of CsCoCl3 revised

Abstract A fine structure of high-field magnetization curves of CsCoCl 3 and related compounds is discussed. It is shown that a precursor of a high-field phase transition originates from nucleation of an intermediate high-field ferrimagnetic (IFM) phase. Since the IFM state is degenerate its growth starting from few nucleation centers gives rise to domain walls formation. Their creep also makes a contribution to the magnetization dynamics similar to slow relaxation in Ca 3 Co 2 O 6 . An experimental verification of the model is proposed.

High-Field Phase Diagram of SmRu4P12Determined by Ultrasonic Measurements in Pulsed Magnetic Field up to 55 T

Elastic constant measurements were performed for the filled skutterudite compound SmRu4P12 in a pulsed magnetic field up to 55 T of \(H\parallel\langle 111\rangle\) to create a high-field phase diagram. The field dependence of the transverse elastic constant \(C_{\text{T}} = (C_{11} - C_{12} + C_{44})/3\) shows two marked anomalies, one of which was assigned as a magnetic transition \(T^{*}\). The other anomaly was newly discovered. The newly discovered phase boundary is immersed in the known phase III, and joins to the known II–III boundary. This particular behavior is compared with the recently proposed theory, and discussed on the basis of the octupole model for this system.

High magnetic field induced phases and half-magnetization plateau in theS=1kagome compound Ni3V2O8

We report on high magnetic field studies of magnetization, electric polarization, and specific heat on single crystals of Ni${}_{3}$V${}_{2}$O${}_{8}$, which is an $S$ $=$ 1 kagome compound. The magnetization process exhibits multistep magnetic transitions when the magnetic field is parallel to the magnetic easy axis. An apparent magnetization plateau was observed at half the height of the saturation magnetization ${M}_{\mathrm{s}}$ \ensuremath{\sim} 2.39\ensuremath{\mu}${}_{\mathrm{B}}$/Ni. In addition, the magnetization transitions at higher fields are quantized at 2/3, 3/4, and 8/9 of ${M}_{\mathrm{s}}$. These results are unusual for the one-third magnetization plateaus that theories have predicted for conventional kagome antiferromagnets. We find that the high magnetic field suppresses the spontaneous polarization, leading to a different high-field phase where the magnetic structure is collinear or coplanar with the underlying lattice. The resulting high-field phase diagram explores several magnetic phases and sheds light on recent experimental findings. Analytical arguments have been presented to discuss these high-field phases.

Neutron diffraction study of the high magnetic field phase diagram of La-doped PrB6

The high magnetic field phase diagram of lanthanum-doped PrB6 was investigated by single-crystal neutron diffraction. In this compound, a peculiar incommensurate phase denoted IC2 was observed in magnetic fields applied along directions close to [111]. Unlike the double-k IC1 phase [kIC1 = (1/4 − δ, ±1/4,1/2)] formed in zero field below TN = 7 K, IC2 is characterized by a propagation vector with two incommensurate components, kIC2 = (1/4−δ′, 1/4 − δ′, 1/2) (δ′ ≊ 0.03). The field and temperature evolutions of domain populations further indicate that, contrary to the low-field phases C and IC1, the magnetic structure in phase IC2 is single-k.

Dilute-bose-gas approach to ground state phases of 3D quantum helimagnets under high magnetic field

We study high-field phase diagram and low-energy excitations of three-dimensional quantum helimagnets. Slightly below the saturation field, the emergence of magnetic order may be mathematically viewed as Bose-Einstein condensation (BEC) of magnons. The method of dilute Bose gas enables an unbiased quantitative analysis of quantum effects in three-dimensional helimagnets and thereby three phases are found: cone, coplanar fan and an attraction-dominant one. To investigate the last phase, we extend the usual BEC approach so that we can handle 2-magnon bound states. In the case of 2-magnon BEC, the transverse magnetization vanishes and long-range order occurs in the quadrupolar channel (spin-nematic phase). As an application, we map out the phase diagram of a 3D helimagnet which consists of frustrated J1-J2 chains coupled by an interchain interaction J3.

Roles of antiferromagnetic fluctuation in high field phase diagram of superconductors with strong paramagnetic depairing

The high field phase diagram and magnetic properties of CeCoIn5 below Hc2(0) are examined from the picture regarding the high field and low temperature (HFLT) phase as a possible Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) vortex lattice. Crucial roles of antiferromagnetic (AFM) fluctuations enhanced close to Hc2(0) are stressed. The FFLO vortex lattice with a longitudinal modulation parallel to the field is stabilized compared with those with lateral modulations as a consequence of the presence of AFM fluctuations. Further, an unusual field-induced enhancement of the flux distribution is argued to be a consequence of interplay between the paramagnetic depairing and AFM fluctuation, both of which are enhanced with increasing field.

Magnon Bose-Einstein condensation and various phases of three-dimensonal quantum helimagnets under high magnetic field

We study high-field phase diagram and low-energy excitations of three-dimensional quantum helimagnets. Slightly below the saturation field, the emergence of magnetic order may be viewed as Bose-Einstein condensation (BEC) of magnons. The method of dilute Bose gas enables a quantitative analysis of quantum effects in these helimagnets and thereby three phases are found: cone, coplanar fan and a phase-separated one. As an application, we map out the phase diagram of a 3D helimagnet which consists of frustrated J1-J2 chains as a function of frustration and an interchain coupling. Moreover, we also calculate the stability of the 2-magnon bound state to investigate the possibility of the bound-magnon BEC.

Observations of the configuration of the high-field vortex lattice inYBa2Cu3O7: Dependence upon temperature and angle of applied field

We have mapped out the high-field phase diagram of the vortex lattice in lightly twinned ${\text{YBa}}_{2}{\text{Cu}}_{3}{\text{O}}_{7}$ by employing small-angle neutron scattering. This extends previous measurements [S. P. Brown et al., Phys. Rev. Lett. 92, 067004 (2004)] in which we reported a transition in local flux-line coordination from distorted triangular to square as a function of field applied parallel to the crystal $c$ axis. At high fields, we observe a transition back to triangular coordination with increasing angle between the applied field and $c$ axis or with increasing temperature. At lower fields, our results may be interpreted in terms of a field-induced reduction of the basal-plane $a\text{\ensuremath{-}}b$ anisotropy. Tilting the flux lines away from the $c$ axis reduces the pinning by twin planes, changes the orientation of the vortex lattice nearest-neighbor directions, and the transition between square and hexagonal vortex lattices becomes first order.