First-order Metamagnetic Transition Research Articles

Magnetocaloric effect and applied refrigeration performance of La(Fe,Si)13-based compounds

As a solid-state refrigeration technology, room-temperature magnetic refrigeration has several significant advantages comparing with conventional gas compression refrigeration, such as environmental friendliness, high energy efficiency and dependable operation. In the present study, the magnetocaloric effect and applied refrigeration performance of La0.8Ce0.2Fe11.6-xMn0.15+xSi1.25Al0.1H1.8 (x = 0, 0.03, 0.06, 0.09, 0.12) compounds were studied systematically. All alloys crystallize mainly in NaZn13-type phase with trace α-Fe phase between 1.36 and 1.80 wt%. The necessary heat treatment improves the formation of main phase. As x increases, the Curie temperature (Tc) decreases gradually from 295.3 K to 273.0 K. All alloys undergo strong field-induced first-order itinerant-electron metamagnetic transition. Under 0–1.5 T, the maximum magnetic entropy changes (-ΔSM)max for La0.8Ce0.2Fe11.6-xMn0.15+xSi1.25Al0.1H1.8 (x = 0, 0.03, 0.06, 0.09, 0.12) compounds vary from 10.9 J/(kg K) to 13.5 J/(kg K). And the maximum adiabatic temperature changes (ΔTad)max vary from 2.7 K to 3.9 K. To study the applied refrigeration performance, a rotary magnetic refrigerator is designed successfully, whose refrigeration temperature and cooling power meet the requirement of cold storage. Successful large-quantity preparation, giant magnetocaloric effect and excellent refrigeration performance suggest that, La0.8Ce0.2Fe11.6-xMn0.15+xSi1.25Al0.1H1.8 (x = 0, 0.03, 0.06, 0.09, 0.12) compounds can be used as the promising candidates for magnetic refrigerants.

Synthesis, structure and properties of RNiBN (R = rare-earth elements)

We report the structural and physical properties of new nitridoborates RNiBN (R = Nd, Sm, Gd, Tb, Dy, Ho, and Er). These compounds crystallize in a tetragonal LaNiBN-type structure with two-dimensional Ni2B2 and RN layers. The physical properties measurements indicate that they are antiferromagnetic metals. For R = Gd and Ho, a successive magnetic transition was observed below N é el temperature, possibly associated with spin re-orientation due to Ruderman-Kittel-Kasuya-Yosida interaction. A giant magnetocaloric effect was measured in the R = Er and Ho compounds, which is related to a field-induced first-order metamagnetic transition from antiferromagnetic to ferromagnetic state. Our results indicate that RNiBN (R = Er and Ho) may be promising candidates for low temperature magnetic refrigeration

Evolution of structure, magnetic phase transition and magnetocaloric effect of GdNiSi1-xAlx (0 ≤ x ≤ 0.3) alloys

The magnetocaloric effects can be enhanced in GdNiSi1-xAlx (0 ≤ x ≤ 0.3) alloys by Al doping. The substitution amount is limited to x = 0.3. GdNiSi and GdNiSi0.9Al0.1 alloys exhibit an antiferromagnetic ground state and the phase transition temperatures are 13 K and 10 K under 0.05 T, respectively. GdNiSi0.8Al0.2 and GdNiSi0.7Al0.3 alloys exhibit a ferromagnetic ground state and the phase transition temperatures are 18 K and 26 K under 0.05 T, respectively. These alloys undergo the field-induced first-order metamagnetic transition from antiferromagnetic to ferromagnetic states. For Δμ0H of 0–7 T, the values of the maximum magnetic entropy change (the relative cooling power) are 7.7 J/kgK (173.1 J/kg), 11.4 J/kgK (303.2 J/kg), 14.3 J/kgK (447.9 J/kg) and 13.0 J/kgK (494.4 J/kg) in GdNiSi1-xAlx (x = 0, 0.1, 0.2 and 0.3) alloys.

Competition of magnetocrystalline anisotropy of uranium layers and zigzag chains inUNi0.34Ge2single crystals

Structural and thermodynamic properties of single-crystalline ${\mathrm{UNi}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{2}$ with $x=0.66$ have been investigated by measuring magnetization, specific heat, and thermal expansion over a wide range of temperatures and magnetic fields. The measurements revealed the emergence of a long-range antiferromagnetic ordering of uranium magnetic moments below the N\'eel temperature ${T}_{\mathrm{N}}=45.5(1)\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and the existence of two easy axes in the studied compound, namely, $b$ and $c$, which correspond to the plane of the uranium zigzag chains. Magnetic field applied along these two crystallographic directions induces in the system a first-order metamagnetic phase transition (from antiferromagnetism to field-polarized paramagnetism), and the width of the magnetic hysteresis associated with that transition reaches as much as about 40 kOe at the lowest temperatures. A magnetic phase diagram developed from the experimental data showed that the metastable region associated with that magnetic hysteresis forms a funnel that narrows toward the N\'eel point in a zero magnetic field. The four-layer Ising model has successfully predicted the collinear antiferromagnetic structure in ${\mathrm{UNi}}_{0.34}{\mathrm{Ge}}_{2}$ (known from earlier reports), its magnetic phase diagram, and temperature and field variations of its magnetization. Moreover, it suggests that the first-order phase transition extends down to a zero magnetic field, although it is barely detectable in the experiments performed in low magnetic fields. According to this model, the second-order phase transition occurs in the compound only in a zero field.

Origin of metamagnetism in skyrmion host Cu_2OSeO_3

Skyrmion host chiral Cu_2OSeO_3 has attracted researchers due to several intriguing properties. Observation of metamagnetism in low-temperature and low-field makes the magnetic properties of Cu_2OSeO_3 more complex. Here, we present an investigation on metamagnetism in Cu_2OSeO_3 by analyzing its structural and magnetic properties. Study of magnetic properties reveal spin-flip of one of the Cu^{2+} ions, embedded in square pyramidal CuO_5 polyhedra, due to the development of strain in low-temperature and low-field regime. The spin-flip is found to be the main reason for field-induced first-order metamagnetic transition. Magnetic phase diagram of Cu_2OSeO_3 has been constructed with the help of magnetization analyses. It is argued that the metamagnetic hysteretic field region may be low-temperature skyrmion phase with additional spiral and tilted-conical phases. A tricritical point has been observed in the phase diagram at which first-order metamagnetic hysteretic field range ceases to exist.

Control of metamagnetic phase transition in epitaxial FeRh films by changing atomic order degree

Near-equiatomic FeRh alloys undergo a first-order metamagnetic phase transition around room temperature. Here, we show that the phase transition parameters of epitaxial FeRh films can be adjusted to a great extent through changing the growth temperature, annealing temperature, and annealing time. The influences of the surface morphology and Fe (Rh) element distribution before and after heat treatments have been analyzed. The experimental results show that the increase of annealing temperature reduces the displacement of Fe (Rh) atoms. As a result, the resistivity is reduced, the phase transition interval is narrowed, and the phase transition is shifted to high temperature. The experimental results indicate that the first-order phase transition parameters in epitaxial FeRh films can be controlled by heat treatments and are correlated with the atomic order degree of Fe (Rh).

Large magnetocaloric effect in antiferromagnetic ternary carbide Dy2Cr2C3 around liquid hydrogen temperature

Field-induced magnetic transitions with large magnetization difference and mitigated thermal loss are highly desirable for the development of magnetocaloric materials used for magnetic refrigeration. Here, we report the magnetocaloric effect (MCE) in antiferromagnetic carbide Dy2Cr2C3. Both the inverse MCE (with positive magnetic entropy change ΔSM) and conventional MCE (with negative ΔSM) have been observed, which are attributed to a field-induced first-order metamagnetic transition from antiferromagnetic to ferromagnetic state and a second-order ferromagnetic to paramagnetic transition, respectively. A maximum -ΔSM of 13.5 J/kg K at 27 K for a field change of 5 T, and correspondingly a refrigerant cooling power of 315 J/kg in a wide working temperature span of 31 K have been achieved. Such a remarkable magnetocaloric response, together with the minor magnetic hysteresis of less than 0.02 T, indicate that Dy2Cr2C3 carbide could be a promising candidate refrigerant for magnetic refrigeration working at temperatures near the liquid H2.

Strain-tunable metamagnetic critical endpoint in Mott insulating rare-earth titanates

Rare-earth titanates are Mott insulators whose magnetic ground state -- antiferromagnetic (AFM) or ferromagnetic (FM) -- can be tuned by the radius of the rare-earth element. Here, we combine phenomenology and first-principles calculations to shed light on the generic magnetic phase diagram of a chemically substituted titanate on the rare-earth site that interpolates between an AFM and a FM state. Octahedral rotations present in these perovskites cause the AFM order to acquire a small FM component -- and vice-versa -- removing any multicritical point from the phase diagram. However, for a wide parameter range, a first-order metamagnetic transition line terminating at a critical endpoint survives inside the magnetically ordered phase. Like the liquid-gas transition, a Widom line emerges from the endpoint, characterized by enhanced fluctuations. In contrast to metallic FMs, this metamagnetic transition involves two symmetry-equivalent and insulating canted spin states. Moreover, instead of a magnetic field, we show that uniaxial strain can be used to tune this transition to zero temperature, inducing a quantum critical endpoint.

Controlling the Metamagnetic Phase Transition in FeRh/MnRh Superlattices and Thin-Film Fe50-xMnxRh50 Alloys.

Equiatomic and chemically ordered FeRh and MnRh compounds feature a first-order metamagnetic phase transition between antiferromagnetic and ferromagnetic order in the vicinity of room temperature, exhibiting interconnected structural, magnetic, and electronic order parameters. We show that these two alloys can be combined to form hybrid metamagnets in the form of sputter-deposited superlattices and alloys on single-crystalline MgO substrates. Despite being structurally different, the magnetic behavior of the alloys with substantial Mn content resembles that of the FeRh/MnRh superlattices in the ultrathin individual layer limit. For FeRh/MnRh superlattices, dissimilar lattice distortions of the constituent FeRh and MnRh layers at the antiferromagnetic-ferromagnetic transition cause double-step transitions during cooling, while the magnetization during the heating branch shows a smooth, continuous trend. For Fe50-xMnxRh50 alloy films, the substitution of Mn at the Fe sites introduces an effective tensile in-plane strain and magnetic frustration in the highly ordered epitaxial films, largely influencing the phase transition temperature TM (by more than 150 K). In addition, Mn acts as a surfactant, enabling the growth of continuous thin films at higher temperatures. Thus, the introduction of hybrid FeRh-MnRh systems with adjustable parameters provides a pathway for the realization of tunable spintronic devices based on magnetic phase transitions.

Enhancement and Discontinuity of Effective Mass through the First-Order Metamagnetic Transition in UTe2

Metamagnetic transitions in the novel spin-triplet superconductor UTe$_2$ were investigated through the newly developed simultaneous measurements of magnetization and sample temperature for the field along the orthorhombic $b$-axis and close to the [011] direction, where reentrant superconductivity (RSC) is detected below and above the first-order metamagnetic transition field $H_{\rm m}$. Combining the Maxwell's relation and the Clausius-Clapeyron equation, we obtained the field dependence of Sommerfeld coefficient $\gamma$ through the first-order metamagnetic transition. A significant enhancement of the effective mass toward $H_{\rm m}$ were detected for both field directions. On the other hand, above $H_{\rm m}$, the effective mass discontinuously decreases for $H~||~b$, while it discontinuously increases for $H~||~\sim [011]$, which seems to make a crucial role for the RSC.

Evidence for a coupled magnetic-crystallographic transition in La0.9Ce0.1Fe12B6

Competition between antiferromagnetic (AFM), paramagnetic (PM), and ferromagnetic (FM) states in ${\mathrm{La}}_{0.9}{\mathrm{Ce}}_{0.1}{\mathrm{Fe}}_{12}{\mathrm{B}}_{6}$ compound is investigated by means of temperature- and magnetic field-dependent x-ray diffraction, magnetization, linear thermal expansion, and magnetostriction experiments. It is shown that both AFM and PM phases get converted into the FM phase via a first-order metamagnetic transition, which is accompanied by a huge forced-volume magnetostriction $\mathrm{\ensuremath{\Delta}}V/V(25\phantom{\rule{0.16em}{0ex}}\mathrm{K},\phantom{\rule{0.16em}{0ex}}6\phantom{\rule{0.16em}{0ex}}\mathrm{T})=1.15%$. X-ray powder diffraction reveals a magnetic field-induced crystallographic phase transition from a $R\overline{3}m$ rhombohedral (AFM, PM) to a $C2/m$ monoclinic (FM) structure. A peculiarly anisotropic lattice expansion as well as giant negative thermal expansion with a volumetric thermal expansion coefficient ${\ensuremath{\alpha}}_{V}=\ensuremath{-}193\ifmmode\times\else\texttimes\fi{}{10}^{--6}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{--1}$ are observed. These findings point to the significance of magnetoelastic effects in this metamagnet and illustrate the strength of the coupling between lattice and spin degrees of freedom in the ${\mathrm{La}}_{0.9}{\mathrm{Ce}}_{0.1}{\mathrm{Fe}}_{12}{\mathrm{B}}_{6}$ intermetallic compound.

Magnetic-field-induced structural phase transition and giant magnetoresistance in La0.85Ce0.15Fe12B6

Magnetoelastic coupling, structural, magnetic, electronic transport, and magnetotransport properties of ${\mathrm{La}}_{0.85}{\mathrm{Ce}}_{0.15}{\mathrm{Fe}}_{12}{\mathrm{B}}_{6}$ have been studied by a combination of macroscopic [magnetization, electrical resistivity, and magnetoresistance (MR)] and microscopic temperature- and magnetic-field-dependent x-ray powder diffraction measurements. The itinerant-electron system ${\mathrm{La}}_{0.85}{\mathrm{Ce}}_{0.15}{\mathrm{Fe}}_{12}{\mathrm{B}}_{6}$ exhibits an antiferromagnetic (AFM) ground state and multiple magnetic transitions, AFM-ferromagnetic (FM) and FM-paramagnetic (PM), triggered by changes in both temperature and magnetic fields. At low temperatures, the field-induced first-order AFM-FM metamagnetic phase transition is discontinuous, manifesting itself by extremely sharp steps in magnetization as well as in MR and is accompanied by large magnetic hysteresis. A remarkably large negative MR of \ensuremath{-}73% was discovered. In addition, the time evolution of the electrical resistivity displays a colossal spontaneous jump when both the applied magnetic field and temperature are constant. Diffraction data reveal a magnetic-field-induced structural phase transition associated with the AFM-FM and PM-FM transformations. The lattice distortion is driven by magnetoelastic coupling and converts the crystal structure from rhombohedral ($R\overline{3}m$) to monoclinic $(C2/m)$. The AFM and PM states are related to the rhombohedral structure, whereas the FM order develops in the monoclinic symmetry. A huge volume magnetostriction of \ensuremath{\sim}0.9% accompanies this symmetry-lowering lattice distortion. Meanwhile, a highly anisotropic thermal expansion involving giant negative thermal expansion with an average volumetric thermal expansion coefficient ${\ensuremath{\alpha}}_{V}=\ensuremath{-}195\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ was observed. The consistency seen in these different experimental data constitutes direct evidence of the strong correlations between charge, magnetic, and crystallographic degrees of freedom in this material.

Magnetic-field-induced avalanches in magnetization and magnetoresistance of La0.9Ce0.1Fe12B6 compound

Competition between paramagnetic (PM), antiferromagnetic (AFM) and ferromagnetic (FM) phases in La0.9Ce0.1Fe12B6 itinerant-electron metamagnetic system is studied by a combination of magnetic, electrical resistivity and magnetoresistance measurements. La0.9Ce0.1Fe12B6 is an antiferromagnet below the Néel temperature (35 K) and presents two consecutive magnetic transitions AFM–FM and FM–PM during warming under certain applied magnetic field values. We further demonstrate that both AFM and PM phases may be converted into the FM phase irreversibly and reversibly via a first-order metamagnetic transition accompanied by a large magnetic field hysteresis. At very low temperatures, the magnetic-field-driven AFM–FM metamagnetic transformation is discontinuous and proceeds by multiple abrupt steps in magnetization and magnetoresistance. In addition, an extraordinarily large negative magnetoresistance (MR) effect of −77% is observed. The consistency found in the magnetotransport and magnetization data suggests strong correlations between charge and spin degrees of freedom in La0.9Ce0.1Fe12B6 system.

Colossal magneto-resistive relaxation effects in La0.9Ce0.1Fe12B6

The study of the magnetic, electronic transport, and magnetotransport properties of La0.9Ce0.1Fe12B6 itinerant-electron system has been performed by combining magnetization, electrical resistivity, and magnetoresistance experiments. Along with the antiferromagnetic (AFM) ordering at TN = 35 K, two consecutive magnetic transformations, antiferromagnetic–ferromagnetic (AFM–FM) and ferromagnetic–paramagnetic (FM–PM), occur upon heating under certain magnetic field values. At fixed temperatures, it is revealed that both AFM and PM phases can be converted into the FM phase irreversibly and reversibly via a first-order metamagnetic transition associated with a large hysteresis. Below 8 K, the metamagnetic transition is discontinuous, manifesting itself by multiple sudden jumps in magnetoresistance and magnetization. A giant negative magnetoresistance effect of about −78% is found. We further demonstrate that the time dependencies of the electrical resistivity and the magnetization exhibit colossal spontaneous steps after an incubation time in conditions where both the applied magnetic field and temperature are constant. Another intriguing observation in the phase diagram is the presence of a critical point at the crossover of the three distinct PM, FM, and AFM magnetic states.

Study on magnetocaloric effect and phase transition in La0.7(La–Ce)0.3FexAl11.5−xSi1.5 alloys

Magnetocaloric materials with high performance are crucial to the achievement of magnetic refrigeration which is a promising cooling technology to replace traditional gaseous compression refrigeration. In this work, the magnetocaloric effect and phase transition of La0.7(La–Ce)0.3FexAl11.5−xSi1.5 alloys have been investigated. The structural and magnetic properties were characterized by means of X-ray diffraction and magnetization measurements. Belov-Arrott plots and the exponent n from field dependence of isothermal entropy change were applied to determine the nature of the phase transition. The XRD patterns indicate that the alloys crystallize mainly in NaZn13-type phase with small amounts of α-Fe and LaFeSi as secondary phases. With an increase of x from 11.0 to 11.4, the Curie temperature decreases from 211.2 K to 185.4 K while the magnetocaloric effect increases from 4.9 J kg−1 ⋅K−1 to 23 J kg−1 ⋅K−1 for a field change of 2 T. The alloys show refrigeration capacity between 111 J ⋅kg−1 and 152 J ⋅kg−1 for a magnetic field of 2 T. Analyses of the Belov-Arrott plot and the exponent of n reveal that the first-order itinerant-electron metamagnetic phase transition in the alloys is weakened by decreasing x, and the alloys with x = 11.2, 11.3 and 11.4 undergo a second-order phase transition.

Magnetocaloric properties and specifics of the hysteresis at the first-order metamagnetic transition in Ni-doped FeRh

Measurements of the magnetization in quasistatic and pulsed magnetic fields with different sweep rates, measurements of the specific heat in various magnetic fields, and direct measurements of the adiabatic temperature change have been employed to study the metamagnetic phase transition from an antiferromagnetic (AF) to the ferromagnetic (FM) state in an ${({\mathrm{Fe}}_{0.98}{\mathrm{Ni}}_{0.02})}_{49}{\mathrm{Rh}}_{51}$ alloy with a critical AF-FM transition temperature, ${T}_{\mathrm{tr}}$, reduced to 266 K. Based on the obtained results, a magnetic phase diagram for this alloy has been constructed. The AF-FM transition induced by the magnetic field below 10 K is found to occur in a steplike fashion in contrast to smooth behavior at $10\phantom{\rule{0.16em}{0ex}}\mathrm{K}<T<{T}_{\mathrm{tr}}$. The adiabatic temperature change $\mathrm{\ensuremath{\Delta}}{T}_{ad}$ in the magnetic field of 2 T exceeds 6.5 K in pulsed fields (\ensuremath{\sim}100 T/s) and in the Halbach setup (\ensuremath{\sim}0.5 T/s), which is in agreement with the estimation from the S-T diagram constructed based on the specific heat measurements. The reversible $\mathrm{\ensuremath{\Delta}}{T}_{ad}$ reaches \ensuremath{-}4.6 K under cyclic conditions in the Halbach setup (2 T). A complete transformation to the FM state in the whole temperature range requires a magnetic field of 14 T. Direct measurements of $\mathrm{\ensuremath{\Delta}}{T}_{ad}$ in pulsed fields of 14 T revealed an irreversible part of the magnetocaloric effect associated with the presence of magnetic hysteresis and respective losses during the magnetization process.

Magnetic imaging and statistical analysis of the metamagnetic phase transition of FeRh with electron spins in diamond

Magnetic imaging based on nitrogen-vacancy (NV) centers in diamond has emerged as a powerful tool for probing magnetic phenomena in fields ranging from biology to physics. A key strength of NV sensing is its local-probe nature, enabling high-resolution spatial images of magnetic stray fields emanating from a sample. However, this local character can also form a drawback for analyzing the global properties of a system, such as a phase transition temperature. Here, we address this challenge by using statistical analyses of magnetic-field maps to characterize the first-order temperature-driven metamagnetic phase transition from the antiferromagnetic to the ferromagnetic state in FeRh. After imaging the phase transition and identifying the regimes of nucleation, growth, and coalescence of ferromagnetic domains, we statistically characterize the spatial magnetic-field maps to extract the transition temperature and thermal hysteresis width. By analyzing the spatial correlations of the maps in relation to the magnetocrystalline anisotropy and external magnetic field, we detect a reorientation of domain walls across the phase transition. The employed statistical approach can be extended to the study of other magnetic phenomena with NV magnetometry or other sensing techniques.

Strain-modulated helimagnetism and emergent magnetic phase diagrams in highly crystalline MnP nanorod films

We explore strain-modulated helimagnetism in highly crystalline MnP nanorod films grown on Si(100) substrates using molecular beam epitaxy. The strained MnP film exhibits a paramagnetic to ferromagnetic (FM) phase transition at ${T}_{C}\ensuremath{\sim}279\phantom{\rule{0.16em}{0ex}}\mathrm{K}$, and the FM to helical phase transition at ${T}_{N}\ensuremath{\sim}110\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The value of ${T}_{N}$ is greater than ${T}_{N}\ensuremath{\sim}47\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ for the MnP single crystal, indicating strong strain-modulated helimagnetic states in the MnP nanorod film. The presence of significant thermal hysteresis in the helical phase indicates the coexistence of competing magnetic interactions, leading to the first-order metamagnetic transition. Similar to its single-crystal counterpart, an anisotropic magnetic effect is observed in the MnP film, which is independently confirmed by magnetic hysteresis loop and radio-frequency transverse susceptibility (TS) measurements. The evolution of the screw to the cone and fan phases is precisely tracked from magnetization vs magnetic field/temperature measurements. The temperature dependence of the anisotropy fields, extracted from the TS spectra, yields further insight into the competing nature of the magnetic phases. Unfolding of the different helical phases at $T<120\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ $(\ensuremath{\sim}{T}_{\mathrm{N}})$ is analyzed by the temperature- and field-dependent magnetic entropy change. Based on these findings, the comprehensive magnetic phase diagrams of the MnP nanorod film are constructed for both the in-plane and out of plane magnetic field directions, revealing emergent strain/dimensionality-driven helical magnetic features that are absent in the magnetic phase diagram of the MnP single crystal.

On Sharp Enhancement of Effective Mass of Quasiparticles and Coefficient of T2 Term of Resistivity around First-Order Metamagnetic Transition Observed in UTe2

The mechanism underlying the enhancement of the Sommerfeld coefficient of quasiparticles at the first-order metamagnetic transition in UTe_2, reported by Miyake et al. in J. Phys. Soc. Jpn. 88, 063706 (2019), is discussed theoretically by taking into account the ferromagnetic order-parameter fluctuations on the basis of the Landau theory of phase transition. We find that the enhanced ferromagnetic spin fluctuation gives rise to the enhancement of the effective mass of the quasiparticles or the Sommerfeld coefficient \gamma,which is consistent with the experimental observations. At the same time, the Kadowaki-Woods type scaling around the metamagnetic transition, reported by Imajo et al.in J. Phys. Soc. Jpn. 88, 083705 (2019) and Knafo et al. in J. Phys. Soc. Jpn. 88, 063705 (2019), is also understood semi-quantitatively by assuming reasonable values of parameters of Landau-type free energy reproducing key quantities characterizing the metamagnetic transition.

Antiferromagnetic ordering in the ternary uranium germanide UNi1–xGe2: Neutron diffraction and physical properties studies

The compound UNi0.45Ge2 was studied by means of X-ray diffraction (XRD), magnetization, neutron diffraction, specific heat and electrical resistivity measurements performed in wide ranges of temperature and magnetic field. The single-crystal XRD experiment indicated that the material crystallizes in the orthorhombic CeNiSi2-type structure with the lattice parameters a = 4.1062(2) Å, b = 15.9272(8) Å and c = 4.0461(2) Å. The physical properties measurements showed that it orders antiferromagnetically at TN = 47 K. The magnetic ordering was confirmed by the neutron diffraction experiment, which revealed that the ordered magnetic moments are aligned along the crystallographic b-axis in a sequence −++−. In strong magnetic fields, a distinct field-induced first-order metamagnetic phase transition occurs, characterized by a large magnetic hysteresis. Temperature and field variations of the electrical resistivity are strongly affected by the atom disorder in the crystallographic unit cell of the investigated compound.