Magnetic Ordering Temperature Research Articles

Magnetic ground state and excitations in the mixed 3d−4d quasi-one-dimensional spin-chain oxide Sr3NiRhO6

Entanglement of spin and orbital degrees of freedom, via relativistic spin-orbit coupling, in 4d transition metal oxides can give rise to a variety of unique quantum phases. A previous study of mixed 3d−4d quasi-1D spin-chain oxide Sr3NiRhO6 using the magnetization measurements by Mohapatra [] revealed a partially disordered antiferromagnetic structure below 50 K. We here report the magnetic ground state and spin-wave excitations in Sr3NiRhO6 using muon spin rotation and relaxation (μSR), and neutron (elastic and inelastic) scattering techniques. Our neutron diffraction study reveals that in the magnetic structure of Sr3NiRhO6 Rh4+ and Ni2+ spins are aligned ferromagnetically in a spin chain, with moments along the crystallographic c axis. However, spin chains are coupled antiferromanetically in the ab plane. μSR reveals the presence of oscillations in the asymmetry-time spectra below 50 K, supporting the long-range magnetically ordered ground state. Our inelastic neutron scattering study reveals gapped quasi-1D magnetic excitations with a large ratio of gap to exchange interaction. The observed spin-wave spectrum could be well fitted with a ferromagnetic isotropic exchange model (with J=3.7 meV) and single ion anisotropy (D=10 meV) on the Ni2+ site. The magnetic excitations survive up to 85 K, well above the magnetic ordering temperature of ∼50 K, also indicating a quasi-1D nature of the magnetic interactions in Sr3NiRhO6. Published by the American Physical Society 2024

Pitfalls of exchange–correlation functionals in description of magnetism: Cautionary tale of the FeRh alloy

The magnetic ground state of FeRh is highly sensitive towards the lattice constant. This, in addition to partially filled d-shells of Fe and Rh, posed a significant challenge for Density Functional Theory (DFT) calculations in the past. Here, we have investigated the performance of various exchange–correlation (XC) functionals within the DFT formalism for this challenging binary alloy. We have employed Local Density Approximation (LDA), various Generalized Gradient Approximations (GGAs), and newly developed Strongly Constrained and Appropriately Normed (SCAN) meta-GGA functional. Our results show the limitations of any single functional in capturing the intricate interplay of structural, electronic, and magnetic properties in FeRh. While SCAN can accurately describe some magnetic features and phonon dispersion, it significantly overestimates the Fe-Fe magnetic interactions, leading to an unreasonable magnetic ordering temperature. Conversely, the Perdew–Burke–Ernzerhof (PBE) GGA exhibits the opposite behavior. These findings highlight the challenges in simulating materials with partially filled d-shells using DFT, underscoring the crucial need for developing a versatile XC functional that can effectively account for the multifaceted nature of such systems.

Large magnetocaloric effect near liquid hydrogen temperatures in Er1-xTmxGa materials

Low-temperature magnetocaloric materials are of great importance for potential applications of gas liquefaction such as nitrogen, hydrogen and helium for their low liquidation temperatures (∼4 K for helium, ∼20 K for hydrogen and ∼77 K for nitrogen respectively), of which the working temperature, the maximal magnetic entropy change ((-ΔSM)max), the maximal adiabatic temperature change ((ΔTad)max), and the temperature average entropy change (TEC) are the key assessment parameters. Herein, we designed and synthesized Er1-xTmxGa series compounds based on the optimization of the spin quantum number (Spin) with their magnetic ordering temperature successfully adjusted from 31.0 K to 15.0 K, which covers the liquid hydrogen temperature range. Particularly, Er0.8Tm0.2Ga shows outstanding (-ΔSM)max, TEC(20), and (ΔTad)max values of 13.6 J/kg K, 10.1 J/kg K, and 4.3 K under the field change of 0–2 T, respectively, which are increased by 32.0 %, 36.4 %, and 48.2 % compared with the parent ErGa compound. It should be noted that the refrigerant capacity (RC) of Er0.8Tm0.2Ga is not only larger than ErGa but also larger than TmGa. Furthermore, neutron powder diffraction (NPD) was employed on Er0.8Tm0.2Ga to reveal the physical mechanism of its enhanced magnetocaloric effect (MCE). It is found that for Er0.8Tm0.2Ga the more pronounced order-to-disorder transition than the spin reorientation (SR) transition, the characteristic second order phase transition, and the existence of the short-range magnetic ordering above the magnetic ordering temperature should be jointly responsible for its large magnetocaloric effect.

Reversible Single-Crystal to Single-Crystal Transformation and Associated Magnetism of a Cyanide-Bridged Chiral-Structured Magnet.

A chiral molecule-based magnet [MnII (S-pnH) (H2O)][MnIII(CN)6]·H2O (S-pn = S-1,2-diaminopropane), 1S·2H2O (P212121), has been obtained, which has a two-dimensional (2D) square network of cyanide-bridged MnII-MnIII ions. The crystallographic research on this coordination polymer indicates that it is robust enough to transform the single-crystal structure upon dehydration as well as rehydration. Meanwhile, the magnetic property changes are reversibly associated with the structural phase transitions. The complete reversibility upon dehydration/rehydration was demonstrated using in situ X-ray diffraction from the as-prepared 1S·2H2O to the dehydrated [MnII (S-pnH)][MnIII(CN)6], 1S, then rehydrated to [MnII (S-pnH) (H2O)][MnIII(CN)6]·H2O, 1S-HP, and dehydrated again to [MnII (S-pnH)][MnIII(CN)6], 1S-DeHP. Neither the space groups nor the crystal axes changed during the dehydration/rehydration process. The dehydration is considered to be associated with a change in the coordination of the S-pnH from one 2D layer to the neighboring one involving a proton transfer and is accompanied by new cyanide bridging of MnII and MnIII ions formed between the 2D sheet. Corresponding to the 2D to three-dimensional (3D) structural transition, the study of magnetic properties reveals that the Curie temperature of long-range magnetic ordering for 1S (TC = 45 K) is more than double that for 1S·2H2O (TC = 21 K).

Thermodynamic evidence for polaron stabilization inside the antiferromagnetic order of Eu5In2Sb6

Materials exhibiting electronic inhomogeneities at the nanometer scale have enormous potential for applications. Magnetic polarons are one such type of inhomogeneity which link the electronic, magnetic and lattice degrees of freedom in correlated matter and often give rise to colossal magnetoresistance. Here, we investigate single crystals of Eu5In2Sb6 by thermal expansion and magnetostriction along different crystallographic directions. These data provide compelling evidence for the formation of magnetic polarons in Eu5In2Sb6 well above the magnetic ordering temperature. More specifically, our results are consistent with anisotropic polarons with varying extent along the different crystallographic directions. A crossover revealed within the magnetically ordered phase can be associated with a surprising stabilization of ferromagnetic polarons within the global antiferromagnetic order upon decreasing temperature. These findings make Eu5In2Sb6 a rare example of such coexisting and competing magnetic orders and, importantly, shed new light on colossal magnetoresistive behavior beyond manganites.

Persistent flat band splitting and strong selective band renormalization in a kagome magnet thin film.

Magnetic kagome materials provide a fascinating playground for exploring the interplay of magnetism, correlation and topology. Many magnetic kagome systems have been reported including the binary FemXn (X = Sn, Ge; m:n = 3:1, 3:2, 1:1) family and the rare earth RMn6Sn6 (R = rare earth) family, where their kagome flat bands are calculated to be near the Fermi level in the paramagnetic phase. While partially filling a kagome flat band is predicted to give rise to a Stoner-type ferromagnetism, experimental visualization of the magnetic splitting across the ordering temperature has not been reported for any of these systems due to the high ordering temperatures, hence leaving the nature of magnetism in kagome magnets an open question. Here, we probe the electronic structure with angle-resolved photoemission spectroscopy in a kagome magnet thin film FeSn synthesized using molecular beam epitaxy. We identify the exchange-split kagome flat bands, whose splitting persists above the magnetic ordering temperature, indicative of a local moment picture. Such local moments in the presence of the topological flat band are consistent with the compact molecular orbitals predicted in theory. We further observe a large spin-orbital selective band renormalization in the Fe spin majority channel reminiscent of the orbital selective correlation effects in the iron-based superconductors. Our discovery of the coexistence of local moments with topological flat bands in a kagome system echoes similar findings in magic-angle twisted bilayer graphene, and provides a basis for theoretical effort towards modeling correlation effects in magnetic flat band systems.

Interplay of pressure and temperature in modulating the magnetic properties of Cr2O3

The spin-lattice interaction is pivotal in tailoring materials properties and is crucial for developing novel spintronic devices. In the current work, we aim to explore the effects of pressure and temperature on the magnetic properties of Cr2O3 to gain insights into its spin-lattice interaction. Through high-pressure neutron diffraction experiments, we observed an enhancement of the magnetic Bragg intensity with increasing pressure and it becomes more pronounced as the temperature increases. Results from first-principles calculations reveal a strengthening of the easy-axis magnetic anisotropy, doubling from 0 to 20 GPa. The exchange parameters, calculated based on this spin orientation, show an enhancement of the dominant magnetic interactions and an increase of magnetic ordering temperature when pressure increases. These findings suggest that the contributions from these two mechanisms are responsible for the observed increase in magnetic Bragg intensity.

Tuning structural modulation and magnetic properties in metal-organic coordination polymers [CH3NH3]CoxNi1-x(HCOO)3.

Three solid solutions of [CH3NH3]CoxNi1-x(HCOO)3, with x = 0.25 (1), x = 0.50 (2) and x = 0.75 (3), were synthesized and their nuclear structures and magnetic properties were characterized using single-crystal neutron diffraction and magnetization measurements. At room temperature, all three compounds crystallize in the Pnma orthorhombic space group, akin to the cobalt and nickel end series members. On cooling, each compound undergoes a distinct series of structural transitions to modulated structures. Compound 1 exhibits a phase transition to a modulated structure analogous to the pure Ni compound [Cañadillas-Delgado, L., Mazzuca, L., Fabelo, O., Rodríguez-Carvajal, J. & Petricek, V. (2020). Inorg. Chem. 59, 17896-17905], whereas compound 3 maintains the behaviour observed in the pure Co compound reported previously [Canadillas-Delgado, L., Mazzuca, L., Fabelo, O., Rodriguez-Velamazan, J. A. & Rodriguez-Carvajal, J. (2019). IUCrJ, 6, 105-115], although in both cases the temperatures at which the phase transitions occur differ slightly from the pure phases. Monochromatic neutron diffraction measurements showed that the structural evolution of 2 diverges from that of either parent compound, with competing hydrogen bond interactions that drive the modulation throughout the series, producing a unique sequence of phases. It involves two modulated phases below 96 (3) and 59 (3) K, with different q vectors, similar to the pure Co compound (with modulated phases below 128 and 96 K); however, it maintains the modulated phase below magnetic order [at 22.5 (7) K], resembling the pure Ni compound (which presents magnetic order below 34 K), resulting in an improper modulated magnetic structure. Despite these large-scale structural changes, magnetometry data reveal that the bulk magnetic properties of these solid solutions form a linear continuum between the end members. Notably, doping of the metal site in these solid solutions allows for tuning of bulk magnetic properties, including magnetic ordering temperature, transition temperatures and the nature of nuclear phase transitions, through adjustment of metal ratios.

Magnetostriction related to skyrmion-lattice formation in chiral magnet FeGe

The B20 type chiral magnet FeGe exhibits the formation of skyrmion-lattice (SkL) phases in the vicinity of the magnetic ordering temperature. The SkL is a magnetic superlattice composed of vortex-type topological spin objects, and it has experimentally been known that its formation requires the existence of an intermediate (IM) phase between SkL and the paramagnetic (PM) phases. We take interest in how the crystal lattice experiences the formation of these topological spin texture. In this study, we observed the so-called spin–orbit coupling induced magnetostriction related to these topological spin texture formation, in addition to the ac magnetization anomalies. The temperature and magnetic field dependences of the lattice parameter reflected the transformation of phases, such as helimagnetic (HM), SkL, IM, conical (CM), and PM phases. In the PM region, a phase characterized as gaseous skyrmions was detected similarly to the case of the same B20 type MnSi. Furthermore, the HM, CM, and IM phases were also divided into two regions. Thus, the precise phase diagram near Tc was reconstructed from the prospect of the magnetostriction such that we demonstrated that the stabilization of skyrmions needs a finite magnetic field.

Signatures of spin-liquid-like state and spin-phonon coupling in square lattice Sr2CuTe0.5W0.5O6

A spin-liquid state can be induced by uncompensated interactions in the spin lattice due to disorder or randomness in exchange pathways. Sr2CuTeO6 and Sr2CuWO6 are square-lattice antiferromagnetic double perovskites (A2BB′O6) with dominant nearest-neighbor (Néel-type) and next-nearest neighbor (Columnar-type) magnetic interactions, respectively. Random distribution of these interactions in a system has been theoretically predicted to be a way to induce the spin-liquid state. Here, we have synthesized a spin-liquid candidate Sr2CuTe0.5W0.5O6 with B′-site mixing of its parent systems (Sr2CuTeO6 and Sr2CuWO6) to explore the phonon properties and their correlations with the liquid-like magnetic interactions. Our measurements reveal the presence of a broad continuum in the Raman spectrum of Sr2CuTe0.5W0.5O6, instead of the well-defined spin-wave excitations (magnon) observed in the parent systems. Observation of continuum feature in the Raman spectrum in conjunction with the lack of long-range magnetic order provide the signatures of liquid-like correlations. On the other hand, phonon anomalies are observed below the short-ranged magnetic ordering temperature indicating the onset of spin-phonon coupling.

Electronic and magnetic phase diagram of Sr2FeO4 at high pressure: A synchrotron Mössbauer study

Transition metal (TM) oxides with high oxidation state TM ions exhibit a variety of unconventional electronic and magnetic states owing to electron correlations effects combined with highly covalent TM–O bonding. Here, we have studied the pressure dependence of electronic state and magnetism of the K2NiF4-type iron(IV) oxide Sr2FeO4 up to 89 GPa by temperature and magnetic field dependent energy-domain synchrotron Mössbauer spectroscopy and derived a (P,T) magnetic phase diagram. Considering also previous resistance studies [Rozenberg , ] several magnetic and electronic regimes with increasing pressure can be identified. Near 7 GPa, the insulating cycloidal antiferromagnetic low-P state is transformed into a semiconducting ferromagnetic state and the magnetic ordering temperature Tm increases from 55 K at ambient pressure to about 100 K at 13 GPa. Between 18 and about 50 GPa the system is ferromagnetic and metallic (FMM) with a strong rise of Tm to above room temperature (RT). Contrary to a recent theoretical study [Kazemi-Moridani , ], the FMM state is attributed to a high-spin t2g3eg1 electronic state with itinerant eg coupled to more localized t2g electrons. Between 50 and 89 GPa a doublet with large quadrupole splitting in the RT Mössbauer spectra indicates a partial high-spin to low-spin (t2g4) transition leading to a decrease in Tm again. The general features of the (P,T) phase diagram of Sr2FeO4 are comparable to those of other simple and A-site ordered iron(IV) perovskite-related oxides with the peculiarity that Sr2FeO4 adopts an insulating state without charge disproportionation of Fe4+ in the low-P region. The high-pressure behavior of Sr2FeO4 and other iron(IV) oxides may be relevant for exploring the role of Hund's physics in multiorbital systems and contributing to the understanding of the electronic situation in unconventional superconductors such as La3Ni2O7 and Sr2RuO4. Published by the American Physical Society 2024

A complex magnetic study: evidence of spin-glass transition below long-range magnetic ordering and its correlation with renormalization of phonon modes

In this paper, we report a complex magnetic behavior arising due to the interplay of three active magnetic cations (Nd/Sm, Co and Ir), forming 3d-5d-4f magnetic sublattices. The B-site ordered double perovskites Nd2CoIrO6and Sm2CoIrO6were successfully prepared by conventional solid-state method. Detailed structural analysis revealed that both samples crystallized in monoclinic structure with P21/n (No.-14) space group. X-ray photoelectron spectroscopy analysis confirms the presence of multiple oxidation states of Ir (i.e. Ir4+and Ir5+). Both samples show a paramagnetic-ferrimagnetic (TFiM) transition around 100 K, additionally, a low temperature transition is observed at around 10 K in the SCIO sample. This FM-like behavior of the samples is attributed to the antiparallel alignment of the Co2+and Ir4+spins, resulting in FiM ordering. The ac susceptibility analysis confirms a spin glass type transition just below the long-range ordering temperature in NCIO sample, The obtained characteristic flipping time of a single spin from both the law (Power law and Vogel-Fulcher law) and nonzero Vogel-Fulcher temperature (T0≃ 89.1 K) further verified the existence of cluster spin-glass behavior below the ordering temperature. The temperature evolution of phonon modes (up to 4 K) suggests that the phonon mode above the magnetic ordering temperature is mainly governed by the lattice degrees of freedom; notable renormalization of the mode frequency below the ordering temperature is due to the coupling of lattice with the underlying magnetic degrees of freedom.

Direct synthesis of controllable ultrathin heteroatoms-intercalated 2D layered materials

Two-dimensional (2D) layered materials have been studied in depth during the past two decades due to their unique structure and properties. Transition metal (TM) intercalation of layered materials have been proven as an effective way to introduce new physical properties, such as tunable 2D magnetism, but the direct growth of atomically thin heteroatoms-intercalated layered materials remains untapped. Herein, we directly synthesize various ultrathin heteroatoms-intercalated 2D layered materials (UHI-2DMs) through flux-assisted growth (FAG) approach. Eight UHI-2DMs (V1/3NbS2, Cr1/3NbS2, Mn1/3NbS2, Fe1/3NbS2, Co1/3NbS2, Co1/3NbSe2, Fe1/3TaS2, Fe1/4TaS2) were successfully synthesized. Their thickness can be reduced to the thinnest limit (bilayer 2D material with monolayer intercalated TM), and magnetic ordering can be induced in the synthesized structures. Interestingly, due to the possible anisotropy-stabilized long-range ferromagnetism in Fe1/3TaS2 with weak interlayer coupling, the layer-independent magnetic ordering temperature of Fe1/3TaS2 was revealed by magneto-transport properties. This work establishes a general method for direct synthesis of heteroatom-intercalated ultrathin 2D materials with tunable chemical and physical properties.

Achieving Magnetic Refrigerants with Large Magnetic Entropy Changes and Low Magnetic Ordering Temperatures.

Adiabatic demagnetization refrigeration (ADR) is a promising cooling technology with high efficiency and exceptional stability in achieving ultralow temperatures, playing an indispensable role at the forefront of fundamental and applied science. However, a significant challenge for ADR is that existing magnetic refrigerants struggle to concurrently achieve low magnetic ordering temperatures (T0) and substantial magnetic entropy changes (-ΔSm) at ultralow temperatures. In this work, we propose the combination of Gd3+ and Yb3+ to effectively regulate both -ΔSm and T0 in ultralow temperatures. Notably, the -ΔSm values for Gd0.1Yb0.9F3 (1) and Gd0.3Yb0.7F3 (2) in the 0.4-1.0 K range exceed those of all previously reported magnetic refrigerants within this temperature interval, positioning them as the most efficient magnetic refrigerants for the third stage to date. Although the -ΔSm values for Gd0.5Yb0.5F3 (3) in 1-4 K are less than those of the leading magnetic refrigerant Gd(OH)F2, the -ΔSm values for Gd0.7Yb0.3F3 (4) in 1-4 K at 2 T surpass those of all magnetic refrigerants previously documented within the same temperature range, making it the superior magnetic refrigerant for the fourth stage identified thus far.

Switching of magnetoelectric states in the Y-type hexaferrite Ba0.5Sr1.5CoMgFe11AlO22

The multiferroic Y-type hexaferrites BaxSr2−xMe2Fe12−yAlyO22 (Me = Zn2+, Co2+, Mg2+, etc.) have attracted much attention due to their giant magnetoelectric (ME) effect up to room temperature and low modulated magnetic field by the chemical doping control of the complex magnetic phases. However, the research of substitution between the Me ions is rare. As doping at the Me ion site can combine the advantages of both, e.g., higher magnetic ordering temperature in Co2 and stronger ME coefficient in Mg2 Y-type hexaferrites, herein, we report the stability and switching of magnetoelectric states in the Y-type hexaferrites Ba0.5Sr1.5CoMgFe11AlO22 single crystals. Our results demonstrate that substituting half of the Mg2+ with Co2+ enhances the transition temperature of the alternating longitudinal conical phase to proper screw spin order up to room temperature compared to those Mg2 Y-type hexaferrites. Simultaneous occurrence of in-plane and out-of-plane ferroelectric polarization is observed, alongside comparable spontaneous magnetization. It was found that the in-plane spin-driven polarization can be reversible below 50 K with a substantial ME coefficient α = −8000 ps/m but becomes irreversible at 100 K. This reversal in the sign of the ME coefficient signifies the transition between two distinct ME states at high temperature. The reversibility and irreversibility of spin-induced polarization are discussed within the framework of free energy based on the ferroelectric phase, which prevail in numerous Y-type hexaferrites. Our results provide insights into understanding the role of the Me ions in the magnetoelectric coupling in Y-type hexaferrites.

Optimization of noncollinear magnetic ordering temperature in Y-type hexaferrite by machine learning

Searching the optimal doping compositions of the Y-type hexaferrite Ba2Mg2Fe12O22 remains a long-standing challenge for enhanced non-collinear magnetic transition temperature (TNC). Instead of the conventional trial-and-error approach, the composition-property descriptor is established via a data driven machine learning method named sure independence screening and sparsifying operator. Based on the chosen efficient and physically interpretable descriptor, a series of Y-type hexaferrite compositions are predicted to hold high TNC, among which the BaSrMg0.28Co1.72Fe10Al2O22 is then experimentally validated. Test results indicate that, under appropriate external magnetic field conditions, the TNC of this composition reaches up to 568 K, and its magnetic transition temperature is also elevated to 735 K. This work offers a machine learning-based route to develop room temperature single phase multiferroics for device applications.

Gadolinium spin dilution in the ferromagnetic solid solutions Gd2–x Y x Cu2Mg

Abstract Samples of the solid solution Gd2–x Y x Cu2Mg (in steps of x = 0.2) were synthesized from the elements in sealed tantalum ampoules in a high-frequency furnace. The polycrystalline samples were characterized by X-ray powder diffraction. The structure of Gd0.988(6)Y1.012(6)Cu2Mg was refined from single-crystal X-ray diffractometer data: Mo2B2Fe type, P4/mbm, a = 762.83(4), c = 375.48(2) pm, wR2 = 0.0277, 285 F 2 values and 13 variables. Single-crystal data gave no hint for Gd/Y ordering. All samples behave like Curie-Weiss paramagnets with stable trivalent gadolinium and ferromagnetic ordering at low temperature. Within the solid solution the Curie temperature drops almost linearly from T C = 113.5(1) K for Gd2Cu2Mg to 9.3(1) K for Gd0.2Y1.8Cu2Mg, allowing a precise adjustment of the magnetic ordering temperature through gadolinium spin dilution.

Synthesis, structure, magnetic and magnetocaloric properties of hydrated terbium antimonate

In recent years, the idea of using magnetic cooling based on the magnetocaloric effect as an alternative to vapor–gas cooling in liquefaction technology has attracted increasing attention from researchers due to its energy efficiency. The aim of the present research was the synthesis of hydrated terbium antimonate promising for magnetic cooling technology by hydrolysis and mechanochemical activation, and complex analysis of the influence of modifying elements on the physicochemical, magnetic and magneticaloric properties and structure of polyantimonic acid. As a result of studies, the methodology for the synthesis of hydrated terbium antimonate has been developed and it has been demonstrated that the phase formation in the fully substituted compound of Tb0.67Sb2O6∙(3 + n)H2O composition occurs after grinding and calcination at 200 °C as a result of ion-exchange reaction. The Curie-Weiss temperature was determined to be θCW = − 5 K. The magnetic ordering temperature has been extrapolated from TP(H) data, as µ0H = 0, to be about 0.98 K, where TP is the minimum of temperature dependences dM/dT curve and varies as a linear function of TP = 2.93·H + 0.98. The values of ΔS and of RC are about 3.8 Jkg−1K−1, 6.2 Jkg−1K− 1 and 18 Jkg−1, 89 Jkg−1 for µ0H = 2 T and 7 T, respectively at T = 3 K.

Magnetic properties of Dy[formula omitted](Co,Ni) compounds at ambient and high pressures

Dy3Co, in addition to two antiferromagnetic (AFM) transitions (35 K and TN∼ 44 K), exhibits a Griffiths-like phase around 65 K and it persists up to ∼1 GPa pressure. External pressure alters the magnetic state significantly and results in increase (decrease) of TN (TAF) by 6.5% (∼13%) with dTN/dP ∼ 3 K/GPa (dTAF/dP ∼ −4.5 K/GPa). Increase in metamagnetic critical field and other changes with pressure indicate the strengthening of AFM interactions in Dy3Co. On the other hand, Dy3Ni shows three magnetic transitions at To∼ 55 K, T1∼ 39 K (AFM) and T2∼ 24 K (AFM). Experimental evidence points to the magnetic ordering temperature to be at To∼55 K instead of 39 K as claimed by certain reports. External pressure reduces (increases) the transition temperature To (T1) by ∼7.9% (7.6%) at a rate of −3.5 K/GPa (2.5 K/GPa). Pressure has only marginal effect on the other low temperature transition at T2. Additionally, ac-susceptibility data exhibit spin-glass like features, which seem to arise from domain wall movements and probably random freezing of small components of spins, coexisting with dominant long-ranged non-collinear AFM structure in these compounds.

Characterization of magnetic properties, including magnetocaloric effect, of RE5Pt2In4 (RE = Gd-Tm) compounds

The RE5Pt2In4 (RE = Gd-Tm) rare earth compounds have been investigated by means of X-ray diffraction (XRD) as well as by DC and AC magnetometric measurements. The compounds crystallize in an orthorhombic crystal structure of the Lu5Ni2In4-type (Pbam space group, No. 55). With decreasing temperature, the intermetallics undergo a transition from para- to ferro-/ferri- (RE = Gd, Tb, Ho, Er) or antiferromagnetic state (RE = Tm). In case of Dy5Pt2In4, the ferromagnetic state is reached through an intermediate antiferromagnetic order present in a limited temperature range. The critical temperatures of magnetic ordering range from 4.1 K (RE = Tm) up to 108 K (RE = Tb). For the majority of investigated compounds, a cascade of additional magnetic transitions is found below the respective critical temperatures of magnetic ordering. The magnetic moments are found solely on the rare earth atoms, while the moments of the remaining Pt and In atoms are absent or are too small to be detected while accompanied by the strong rare earth’s moments. The magnetocaloric (MCE) performance of RE5T2In4 (RE = Gd-Tm) is found quite good, especially while taking into account the compounds with RE = Ho and Er. Maximum magnetic entropy change (−ΔSMmax) reaches 11.8 (RE = Ho) or 11.4 J ⋅ kg−1 ⋅ K−1 (RE = Er) under magnetic flux density change of 0–9 T. Under the same conditions, the relative cooling power (RCP) and refrigerant capacity (RC) equal 607 and 495 J ⋅ kg−1 (RE = Ho) or 434 and 341 J ⋅ kg−1 (RE = Er).