Field-induced Metamagnetic Transition Research Articles

Direct and inverse magnetocaloric effects in magnetostrictive GdMn2Ge2 with field-induced metamagnetic transition

Heavy rare-earth-based ternary intermetallic compounds with the formula RT2X2 have drawn great interest because of their multiple magnetic transitions and various magnetic structures. Here, anisotropic magnetic behaviors, magnetocaloric effects (MCEs), and magnetostriction effects in single-crystalline GdMn2Ge2 are studied in two different directions. Experiments show a magnetic transition characterized by a sudden decrease in magnetization for μ0H//a and a sharp increase for μ0H//c at Tt. The transition is driven by lower temperatures for μ0H//a, contrasting that for μ0H//c with an increase in the magnetic field. An inverse MCE is observed for μ0H//a with a maximum magnetic entropy change (−ΔSMmax) of −7.4 J kg−1 K−1 (μ0ΔH = 6 T), while a direct MCE is obtained for μ0H//c with an −ΔSMmax of 8.0 J kg−1 K−1 under the same magnetic field change. Moreover, a remarkable field-induced metamagnetic transition and a magnetostriction effect are observed simultaneously at Tt, indicating strong magneto-lattice coupling. The T-μ0H phase diagrams are constructed based on the magnetic properties. The coexistence of direct and inverse MCEs is discussed and is due to the spin-flop of Mn and anisotropic magnetic properties under magnetic fields in different directions.

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.

Magnetism and magnetocaloric effects in tetragonal structure of RE5Ni2Sb (R = Er, Ho) compounds

In this work, the RE5Ni2Sb (RE = Er, Ho) compounds with tetragonal structure were successfully synthesized and the magnetism, magnetic phase transition and magnetocaloric effects were investigated. It was demonstrated that antiferromagnetic interaction undergoes a field-induced metamagnetic transition from antiferromagnetism to ferromagnetism in RE5Ni2Sb (RE = Er, Ho) under a magnetic field higher than 3 T. Moreover, the Er5Ni2Sb and Ho5Ni2Sb undergo an antiferromagnetic to paramagnetic magnetic phase transition at approximately 18 K and 25 K, and exhibit considerable magnetocaloric effects. The maximum magnetic entropy changes are 9.8 J/kg K and 10.6 J/kg K under varying magnetic fields of 0–5 T. Therefore, the large reversible MCE under low magnetic field change indicates the potential application of RE5Ni2Sb (RE = Er, Ho) in hydrogen liquefaction magnetic refrigerators. Prime Novelty StatementThis work investigates the synthesis, magnetism, and magnetothermal effects of R5Ni2Sb (R = Er, Ho) compounds. The R5Ni2Sb (R = Er, Ho) compounds have been demonstrated for the first time to have a potential application as magnetic refrigeration materials.

Magnetic field-induced narrow first-order and metamagnetic phase transitions of Nd5Ge3

We report on the magnetic behaviour of Nd5Ge3 by investigating through magnetization, neutron diffraction and muon spin relaxation measurements. Temperature dependent-magnetization, muon depolarization rate (λ), initial asymmetry (A0) and the stretched exponent (β) show a clear anomaly at the Néel temperature TN ∼ 54 K. However, the short-range correlated ferromagnetic interactions below TN are inferred from the diffuse scattering mechanism as revealed by zero-field neutron diffraction data. Narrow first order phase transition is due to the competing interaction of a high temperature weak-antiferromagnetic and low temperature glassy states. Magnetic field-induced reentrant spin glass state from a magnetic glass state is observed, before it transforms to a ferromagnetic state.

Giant low-field magnetocaloric effect in unstable antiferromagnetic Tm1–xErxNi2Si2 (x = 0.2, 0.4) compounds

Magnetic refrigeration (MR) technology is regarded as an ideal solution for cryogenic applications, relying on magnetocaloric materials which provide necessary chilling effect. A series of polycrystalline Tm1–xErxNi2Si2 (x = 0.2, 0.4) compounds was synthesized, and their magnetic properties, magnetic phase transition together with magnetocaloric effect (MCE) were studied. The Tm1–xErxNi2Si2 (x = 0.2, 0.4) compounds display a field-induced metamagnetic transition from antiferromagnetic (AFM) to ferromagnetism (FM) in excess of 0.2 T, respectively. Meanwhile, the AFM ground state is unstable. Under the field change of 0–2 T, the values of maximal magnetic entropy change (−ΔSMmax) and refrigerant capacity (RC) for Tm0.8Er0.2Ni2Si2 compound are 17.9 J/(kg·K) and 83.5 J/kg, respectively. The large reversible MCE under low magnetic fields (≤2 T) indicates that Tm0.8Er0.2Ni2Si2 compound can serve as potential candidate materials for cryogenic magnetic refrigeration.

Spin-phonon coupling driven magnetodielectric effect in low-dimensional complex magnetic BaGdFeO4 system

In this report, we have investigated the detailed magnetodielectric properties associated with spin-phonon coupling in the BaGdFeO4 polycrystalline compound, X-ray diffraction study confirms the orthorhombic crystal structure with a space group of Pnma. The DC magnetization measurements indicate the complex magnetic behavior with multiple magnetic transitions at TN1 = 62 K and TN2 = 31 K. In the field-dependent magnetization study, field-induced metamagnetic transitions and their temperature dependence have been attributed to the competing magnetic interactions of two magnetic sub-lattices with rare-earth (Gd3+) and Fe3+ magnetic spins. Dielectric measurements have revealed the correlation of observed dielectric anomalies with the magnetic transitions. The frequency-independent and magnetic field-dependent dielectric anomalies, along with the corresponding magnetic transitions, thus corroborate the subtle magnetodielectric coupling studied by temperature-dependent magnetodielectric measurements. We discuss possible origins for the magnetodielectric behavior in terms of weak spin-phonon interactions, as confirmed by the temperature-dependent Raman spectra measurements.

Fe doping induced cluster/spin glass state and metamagnetic transition in phase separated La0.5Sr0.5Mn1−xFexO3

We report the impurity doping effects in manganites La0.5Sr0.5Mn1−xFexO3 (0 ≤ x ≤ 0.2) and the field-induced metamagnetic transition in which the antiferromagnetic insulating phase transforms into ferromagnetic metallic phase. The Rietveld refined results of XRD data display no obvious structure change with a significant degree of Fe3+ doping on Mn sites. Significant ferromagnetism suppression and magnetic inhomogeneity tendency upon Fe3+-doping are evidenced, phase separated and spin-glass like states are identified. With applying a pulsed high magnetic field up to 50 T, a metamagnetic transition was induced, especially clear for x ≥ 0.1 compounds, which exhibited an irreversible phase transition from antiferromagnetic to ferromagnetic phase, and a saturation magnetization was obtained. The replacement of Mn3+ by Fe3+ ions eliminates the effects of lattice structure change on the magnetic and electronic properties because of the very similar ionic size of Mn3+ and Fe3+, but reduces the Mn3+/Mn4+ ratio and depopulates the number of available hopping sites and the hopping electrons, thus weakens the double exchange interaction. The occurrence of the AFM superexchange interaction via Fe3+–O2−–Fe3+ and Fe3+–O2−–Mn3+ bonds may bring about the competition between the antiferromagnetic ordering and the ferromagnetic ordering, leading to a cluster/spin-glass behavior in the samples with high Fe dopants concentration.

Highly Anisotropic Magnetism and Nearly Isotropic Magnetocaloric Effect in Mn3Sn2 Single Crystals

Mn3Sn2 has been proposed as an ideal material for magnetic refrigeration. It undergoes two successive ferromagnetic transitions (T C1 = 262 K and T C2 = 227 K) and one antiferromagnetic transition (T N = 192 K). Herein we report, for the first time, the preparation of single crystals of Mn3Sn2 from Bi flux. The resultant anisotropic magnetic properties and magnetocaloric effect are investigated along the three principal crystallographic directions of the crystal. Significant anisotropy of magnetic susceptibility and multiple field-induced metamagnetic transitions were found at low fields, whereas the magnetocaloric effect was found to be almost isotropic and larger than that of the polycrystalline one. The maximum magnetic entropy change amounts to −ΔS M = 4.01 J⋅kg−1⋅K−1 near T C1 under a magnetic field change of μ 0ΔH = 5 T along the c-axis, with the corresponding refrigerant capacity of 1750 mJ⋅cm−3. Combined with a much wider cooling temperature span (∼ 80 K), our results demonstrate Mn3Sn2 single crystal to be an attractive candidate working material for active magnetic refrigeration at low temperatures.

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

Coupled magnetic and structural transition in topological antiferromagnet EuAgAs under high pressure

Recently, EuAgAs and its derivatives have emerged as a promising platform for studying the interplay of transports, magnetism and topology. Herein, we report construction of a temperature-pressure phase diagram for antiferromagnetic Dirac semimetal EuAgAs, through electrical transport, synchrotron x-ray diffraction and Raman spectroscopy measurements in diamond anvil cells at high pressures up to 48.6 GPa. At Pc1∼3–5 GPa, we found a pressure-induced magnetic phase transition with accompanying a structural P63/mmc→Pnma transition. In the pristine antiferromagnetic phase, negative colossal magnetoresistance is observed mainly below the Néel temperature TN along with a field-induced metamagnetic transition; in the emergent magnetic phase, however, it is evident both above and below the magnetic critical temperature TC yet with no field-induced metamagnetic transition. These distinct features lead us to argue a ferromagnetic-like state for EuAgAs above Pc1, which is further supported by observation of a T5/3 temperature dependence of low-temperature resistance, a characteristic of marginal Fermi-liquid state expected to exist close to a ferromagnetic instability by spin fluctuations in metallic ferromagnets. At Pc2∼20 GPa, a possible phase transition of electronic origin may take place, which is revealed jointly by change of a T5/3→T5/2 temperature dependence of low-temperature resistance and change in slope of linear-in-T resistance at high temperatures.

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.

Effect of Co doping on structural and magnetic properties of kagome like La based cuprate francisite Cu3La(SeO3)2O2Cl

The effects of Co doping on the structural and magnetic properties of a frustrated layered rare earth based synthetic analog of mineral francisite [Cu3La(SeO3)2O2Cl;(LaCufr)] have been investigated experimentally with a prior theoretical input. We have estimated intra-layer and inter-layer exchange interactions from density functional theory, which reveals the strong antiferromagnetic (AFM) nature of the studied compounds. 10 at. % Co-doped CuLafr confirms incorporation of Co2+ at the Cu2+ site with the local environment around dopant Co nearly similar around that of host Cu. An observed field-induced meta-magnetic transition and a spin reorientation transition have been interpreted considering magnetic exchange interactions. Co-doped LaCufr exhibits a decrease in the AFM ordering temperature and the critical field corresponding to a meta-magnetic spin-flip type transition. The competition and modulation among different intra-layer exchange interactions upon incorporation of Co into the Cu site may lead to such situations. The evidence of spin–phonon coupling from Raman analysis in both compounds is noteworthy and enriches their magnetic properties.

Competing Magnetic Interactions and Field-Induced Metamagnetic Transition in Highly Crystalline Phase-Tunable Iron Oxide Nanorods.

The inherent existence of multi phases in iron oxide nanostructures highlights the significance of them being investigated deliberately to understand and possibly control the phases. Here, the effects of annealing at 250 °C with a variable duration on the bulk magnetic and structural properties of high aspect ratio biphase iron oxide nanorods with ferrimagnetic Fe3O4 and antiferromagnetic α-Fe2O3 are explored. Increasing annealing time under a free flow of oxygen enhanced the α-Fe2O3 volume fraction and improved the crystallinity of the Fe3O4 phase, identified in changes in the magnetization as a function of annealing time. A critical annealing time of approximately 3 h maximized the presence of both phases, as observed via an enhancement in the magnetization and an interfacial pinning effect. This is attributed to disordered spins separating the magnetically distinct phases which tend to align with the application of a magnetic field at high temperatures. The increased antiferromagnetic phase can be distinguished due to the field-induced metamagnetic transitions observed in structures annealed for more than 3 h and was especially prominent in the 9 h annealed sample. Our controlled study in determining the changes in volume fractions with annealing time will enable precise control over phase tunability in iron oxide nanorods, allowing custom-made phase volume fractions in different applications ranging from spintronics to biomedical applications.

The effects of Cu substitution on magnetocaloric effects of the HoCo1−xCuxSi (0 ≤ x ≤ 0.4) phases

By hetero-structural alloying ferromagnetic (FM) TiNiSi-type orthorhombic HoCoSi with antiferromagnetic (AFM) Ni2In-type hexagonal HoCuSi, the magnetic and structural evolutions have been observed in HoCo1−xCuxSi (0 ≤ x ≤ 0.4) alloys. The magnetic property is changed from ferromagnetic for x ≤ 0.3 to antiferromagnetic for x = 0.4 in HoCo1−xCuxSi system. With the field change Δμ0H = 5 T, the maximum magnetic entropy changes (−ΔSMmax) are 10.1 J kg−1 K−1, 8.6 J kg−1 K−1, 7.6 J kg−1 K−1, 10.0 J kg−1 K−1 and 13.6 J kg−1 K−1 in HoCo1−xCuxSi (x = 0, 0.1, 0.2, 0.3 and 0.4) alloys, respectively. With the enhancement of substitution amount, the −ΔSMmax is decreased for x ≤ 0.2, which is caused by magnetic moment dilution effects. But the −ΔSMmax is increased for 0.3 ≤ x ≤ 0.4, which is caused by the field-induced metamagnetic transition at the critical component.

Correlated temperature and field dependent magnetization: Enhanced magnetic hysteresis upon Dy doping in La-based francisite Cu3La(SeO3)2O2Cl

Study of La-based cuprate francisite (LaCufr), an analogue compound of Cu3Bi(SeO3)2O2Cl, is interesting due to the interplay of competing magnetic interactions in this geometrically frustrated layered compound. The motivation is to investigate the role of rare earth metals with 4f electrons on Cu2+ ions with 3d electrons, i.e., to study a complex 3d-4f interaction. In this regard, pristine, 5, and 10 at% (atomic percentage) Dy doped La-based cuprate francisite [Cu3La1-xDyx(SeO3)2O2Cl; x = 0, 0.05, and 0.1] compounds were synthesized. Structural (X-ray diffraction i.e. XRD), electronic (X-ray absorption near edge structure i.e. XANES) and magnetic properties were investigated. XRD and XANES ensure phase purity and indicate dopant Dy atoms are more or less substitutionally incorporated at the La site. Magnetic properties were highlighted by unconventional magnetic hysteresis due to spin reorientation transition (SRT) and field-induced meta-magnetic transition (MMT) below 15 K. The signature of MMT was also observed from a temperature dependent magnetization (M−T) study, which is unique. The process of field dependent magnetization has been explored with a spin flop and spin flip transition. Dy doping enhances hysteresis and overall magnetization. The reason for this enhancement has been interpreted as identifying micro-interactions using an energy splitting scheme.

Anisotropic magnetic property, magnetostriction, and giant magnetocaloric effect with plateau behavior in TbMn2Ge2 single crystal

The ternary RMn2Ge2 (R = rare earth) intermetallic compounds have attracted great attention due to their interesting magnetic behaviors and magnetotransport responses. Here, we reported our observation of anisotropic magnetic property, magnetostriction, and magnetocaloric effect (MCE) in TbMn2Ge2 single crystal. Below the transition temperature of Tb magnetic sublattices (T_{{text{C}}}^{{{text{Tb}}}} ~ 95 K), strong Ising-like magnetocrystalline anisotropy is observed with an out-of-plane ferromagnetic moments 5.98 μB/f.u. along the easy c axis, which is two orders of magnitude larger than that of field along a axis. Above T_{{text{C}}}^{{{text{Tb}}}}, a field-induced metamagnetic transition is observed from the spin-flip of Mn sublattices. During this transition, remarkable magnetostriction effect is observed, indicating of strong spin–lattice coupling. The responses of Tb and Mn sublattices to the magnetic field generate a giant magnetic entropy change (- Delta S_{M}) and large values of relative cooling power (RCP) and temperature-averaged entropy change (TEC). The calculated maximum magnetic entropy change (- Delta S_{M}^{max }), RCP, and TEC(10) with magnetic field change of 7 T along c axis reach 24.02 J kg−1 K−1, 378.4 J kg−1, and 21.39 J kg−1 K−1 near T_{{text{C}}}^{{{text{Tb}}}}, which is the largest among RMn2Ge2 families. More importantly, this giant MCE shows plateau behavior with wide window temperatures from 93 to 108 K, making it be an attractive candidate for magnetic refrigeration applications.

Incommensurate spin density wave and magnetocaloric effect in the metallic triangular lattice HoAl2Ge2

We report the magnetic structure and the magnetocaloric effect (MCE) of the ternary compound $\mathrm{Ho}{\mathrm{Al}}_{2}{\mathrm{Ge}}_{2}$ with a trigonal ${\mathrm{CaAl}}_{2}{\mathrm{Si}}_{2}$-type crystal structure. A neutron powder diffraction experiment reveals that $\mathrm{Ho}{\mathrm{Al}}_{2}{\mathrm{Ge}}_{2}$ exhibits an incommensurate spin density wave (SDW) with a propagation vector $\mathbit{k}=(0.23,\phantom{\rule{0.28em}{0ex}}0,\phantom{\rule{0.28em}{0ex}}0.06)$. The special arrangement of magnetic moments in $\mathrm{Ho}{\mathrm{Al}}_{2}{\mathrm{Ge}}_{2}$ induces interesting physical phenomena and large magnetocaloric effects. The rise in resistivity at low temperatures indicates the effect of the SDW state in the electronic transport. The maximum magnetic-entropy change is $\ensuremath{-}16.1\phantom{\rule{0.16em}{0ex}}\mathrm{J}/\mathrm{kg}\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ under a magnetic field change of 0--70 kOe for an isotropic $\mathrm{Ho}{\mathrm{Al}}_{2}{\mathrm{Ge}}_{2}$ powder and it increases to $\ensuremath{-}17.9\phantom{\rule{0.16em}{0ex}}\mathrm{J}/\mathrm{kg}\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ for a single crystal when the magnetic field ($H$) is applied parallel to the $ab$ plane. A large rotating magnetic-entropy change of $\ensuremath{-}5.1\phantom{\rule{0.16em}{0ex}}\mathrm{J}/\mathrm{kg}\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ for $H=20\phantom{\rule{0.16em}{0ex}}\mathrm{kOe}$ in a $\mathrm{Ho}{\mathrm{Al}}_{2}{\mathrm{Ge}}_{2}$ single crystal is obtained, which is closely associated to the magnetic anisotropy of the SDW order and its response to the external magnetic field. We discuss the large MCE in terms of the field-induced metamagnetic transition from the incommensurate SDW order to the ferromagnetic order. Our study establishes the triangular lattice $R{\mathrm{Al}}_{2}{\mathrm{Ge}}_{2}$ ($R$ = rare-earth elements) as a unique family of compounds to explore the existence of the incommensurate spin density waves and the correlated physical properties.

Anisotropic magnetic properties and tunable conductivity in two-dimensional layered NaCrX2 (X=Te,Se,S) single crystals

Monolayer NaCrX2 (X=Te,Se,S) were theoretically proposed to be two-dimensional intrinsic ferromagnetic semiconductors while their physical properties have not been thoroughly investigated in bulk single crystals. We report the single-crystal growth, structural, magnetic and electronic transport properties of NaCr(Te1-xSex)2 (0 6 x 6 1) and NaCrS2. For NaCr(Te1-xSex)2, the strong perpendicular magnetic anisotropy of NaCrTe2 can be gradually tuned to be a nearly isotropic one by Se-doping. Meanwhile, a systematic change in the conductivity with increasing x is observed, displaying a doping-induced metal-insulator-like transition. Under magnetic field larger than 30 koe, both NaCrTe2 and NaCrSe2 can be polarized to a ferromagnetic state. While for NaCrS2, robust antiferromagnetism is observed up to 70 kOe and two field-induced metamagnetic transitions are identified along H||ab. These intriguing properties together with the potential to be exfoliated down to few-layer thickness make NaCrX2 (X=Te,Se,S) promising for exploring spintronic applications.

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.

Magnetocaloric effect in ScGdTbDyHo high-entropy alloy: Impact of synthesis route

Magnetic energy conversion systems based on magnetocaloric effect promise to be an efficient and eco-friendly alternative to widespread gas cooling systems. Progress in this field initiates an active search for high-performance magnetic refrigerants with suitable characteristics. Among various caloric materials, rare-earth multi-principal element alloys are of particular interest to achieve these purposes. Since structure and properties in these materials strongly depend on synthesis conditions and fabrication prehistory, these issues need to be considered for each multi-element systems. This study is aimed to address structure formation, magnetic and magnetocaloric properties in ScGdTbDyHo high-entropy alloy fabricated under different conditions. We analyze the liquid and solid phases in this system using the ab initio molecular dynamics simulations and find that the alloy has a strong tendency to form a single-phase solid solution. Within the experimental study, as-cast, rapidly quenched, thermally annealed and severely cold-deformed alloy samples have been examined. We have found that all the fabricated specimens are single-phase hexagonal close-packed solid solutions characterized by different density of structural defects. The magnetic measurements reveal a complex magnetic structure in these materials. The Neel point in the studied alloys varies in the range of 139–144 K. A field-induced metamagnetic transition from antiferromagnetic to ferromagnetic state is observed in the alloy samples at all temperatures below the Neel point. In the magnetically ordered state, all the materials demonstrate large coercive force, reaching 4 kOe. Despite of the magnetic hysteresis, the alloys demonstrate the largest values of relative cooling power (920–984 J/kg at 5 T magnetic field) among similar rare-earth high-entropy systems reported so far. Analysis of the experimental results obtained for the alloy samples fabricated under different synthesis conditions allows us to conclude that there is a correlation between structural defectiveness and refrigerant capacity in this rare-earth system.