Rare-earth Sublattice Research Articles

Spin reorientation and the interplay of magnetic sublattices in Er2CuMnMn4O12.

Through a combination of magnetic susceptibility, specific heat, and neutron powder diffraction measurements we have revealed a sequence of four magnetic phase transitions in the columnar quadruple perovskite Er2CuMnMn4O12. A key feature of the quadruple perovskite structural framework is the complex interplay of multiple magnetic sublattices via frustrated exchange topologies and competing magnetic anisotropies. It is shown that in Er2CuMnMn4O12, this phenomenology gives rise to multiple spin-reorientation transitions driven by the competition of easy-axis single ion anisotropy and the Dzyaloshinskii-Moriya interaction; both within the manganese B-site sublattice. At low temperature, one Er sublattice orders due to a finite f-d exchange field aligned parallel to its Ising axis, while the other Er sublattice remains non-magnetic until a final, symmetry-breaking phase transition into the ground state. This non-trivial low-temperature interplay of transition metal and rare-earth sublattices, as well as an observed k = (0, 0, ½) periodicity in both manganese spin canting and Er ordering, raises future challenges to develop a complete understanding of the R2CuMnMn4O12 family.

Structural order and disorder within novel antiferromagnetic RCrxGa3-yGey and R4Cr1-xGa12-yGey intermetallic compounds (R = Tb, Dy)

Single crystals of intermetallic phases RCrxGa3−yGey (R = Tb, Dy; x = 0.19–0.23, y = 0–0.4) and R4Cr1−xGa12−yGey (R = Tb, Dy; x = 0–0.13, y = 3–4) were grown from Ga flux ensuring the absence of magnetic impurities. The X-ray diffraction experiments revealed that the compounds belong to the family of filled AuCu3-type gallides. The compounds are formed upon the insertion of Cr atoms into E6 octahedral voids (E = Ga/Ge), which can occur in either disordered (RCrxGa3-yGey) or ordered (R4Cr1-xGa12-yGey) fashion. The unique feature of the obtained compounds is the strong correlation between the level of Ge doping and the Cr concentration in the phases, which allows one to control both the structural and magnetic ordering. At low Ge concentration, the cubic RCrxGa3-yGey phases form, which then experience tetragonal distortion upon the increase in the Ge content, and the cubic R4Cr1-xGa12-yGey 2×2×2 superstructures are formed at even higher Ge concentrations. The X-ray diffraction analysis also showed a presence of structural defects in the phases, which are caused by different size of empty E6 and filled CrE6 octahedra. Magnetic measurements of the single crystals of the cubic phases reveal antiferromagnetic ordering of the rare earth sublattice with the Neel temperatures decreasing upon Ge doping from 22 K for RCrxGa3 to 10 K for R4Cr1−xGa12−yGey. The Ge doping causes gradual decrease in the strength of antiferromagnetic R-R interactions ultimately leading to noncollinear magnetic structure in the superstructure R4Cr1−xGa12−yGey phases.

Synthesis, magnetic and superconducting properties of high-entropy rare-earth boride (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)(Rh,Ru)4B4

We report the structure and physical properties of a new rare-earth (RE) high-entropy boride (HEB) (Dy0.2Ho0.2Er0.2Tm0.2Lu0.2)(Rh0.85Ru0.15)4B4. The as-cast HEB consists of a highly crystallized, body-centered-tetragonal phase (I41/acd, a = 7.460 Å and c = 14.860 Å); here, all the RE elements share the same crystallographic site and are distributed uniformly on both macroscopic and microscopic scales. At high temperature, the HEB shows a paramagnetic behavior with a large effective moment peff yet it becomes a bulk superconductor upon cooling below 6.0 K. Remarkably, a peculiar cocktail effect of properties is observed: while the lattice parameters, Tc and peff of the HEB agree reasonably well with the compositional averages of the individual pseudo-ternary counterparts, the increased RE mixing entropy tends to suppress the superconductivity even without the magnetic exchange interactions, and a reentrant resistive transition is induced at magnetic fields above 0.8 T. Our results indicate that the high-entropy design of the RE sublattice is a viable way to tune the electrical and magnetic properties in RE intermetallics.

Negative magnetization and magnetic ordering of rare earth and transition metal sublattices in NdFe0.5Cr0.5O3

We investigate the effect of alloying at the 3d transition metal site of a rare-earth-transition metal oxide, by considering NdFe0.5Cr0.5O3 mixed perovskite with two equal and random distribution of 3d ions, Cr and Fe, interacting with an early 4f rare earth ion, Nd. Employing temperature- and field- dependent magnetization measurements, temperature-dependent x-ray diffraction, neutron powder diffraction, and Raman spectroscopy, we characterize its structural and magnetic properties. Our study reveals bipolar magnetic switching (arising from negative magnetization) and magnetocaloric effect which underline the potential of the studied mixed perovskite in device application. The neutron diffraction study shows the absence of spin reorientation transition over the entire temperature range of 1.5–320 K, although both parent compounds exhibit spin orientation transition. We discuss the microscopic origin of this curious behavior. The neutron diffraction results also reveal the ordering of Nd spins at an unusually high temperature of about 40 K, which is corroborated by Raman measurements.

Metamagnetic phase transition induced large magnetocaloric effect in a Dy0.5Ho0.5MnO3 single crystal.

Magnetic refrigeration based on the magnetocaloric effect is gaining interest in orthogonal or hexagonal rare-earth manganite. However, a more comprehensive understanding of the underlying mechanism is still required. We grew a high-quality single crystal of Dy0.5Ho0.5MnO3 using the optical floating zone method, since the parent crystals DyMnO3 and HoMnO3 have orthogonal and hexagonal structures, respectively. The magnetic and magnetocaloric properties and refrigeration mechanisms are thoroughly investigated. Doping modifies the magnetism according to the results obtained from the investigation of magnetic and dielectric properties and heat capacity. The spin reorientation transition shifts towards low temperature in comparison to HoMnO3. Near the Néel temperature of rare-earth sublattices (5 K), the highest changes in negative magnetic entropy under 0-70 kOe are 18 J kg-1 K-1 and 13 J kg-1 K-1 along the a- and c-axes, respectively. The low-temperature metamagnetic phase transition caused by the alterations in the magnetic symmetry of Ho3+ contributes to an increased magnetocaloric effect in comparison to the parent crystals, rendering it a promising choice for magnetic refrigeration applications. Dy0.5Ho0.5MnO3 exhibits a clear magnetocrystalline anisotropy with enhanced refrigeration capacity and negative magnetic entropy change along the a-axis. The adiabatic temperature change of Dy0.5Ho0.5MnO3 is 8.5 K, larger than that of HoMnO3, rendering it a promising choice for low-temperature magnetic refrigeration applications.

Magnetic structures and properties of new 1:1 MoB-type RCo0.6Ni0.4 and RCo0.5Ni0.5 (R = Tb, Dy, Ho): Structural transition induced by magnetic ordering

The magnetic properties, the crystal and the magnetic structures of the new 1: 1 RCo1−xNix phase formed by R = Tb, Dy and Ho, have been studied for x = 0.4 and 0.5 by means of physical property measurements, neutron and X-ray (from both laboratory and synchrotron) diffraction methods. These compounds crystallize in the tetragonal MoB structure type (tI16, I41/amd) at room temperature, with no ordered arrangement of Co/Ni atoms on the 8e Wyckoff site available for the transition element. Both the lattice parameters a and c (and unit cell volume, Vobs) decrease from Tb to Ho, with a and c following a linear and a quadratic trend, respectively. A magnetic phase transition is detected by heat capacity and magnetization data for TbCo0.6Ni0.4 at about 85 K. Similar transitions appear in DyCo0.6Ni0.4 and HoCo0.6Ni0.4 at 49 K and 27 K, respectively. These TC well follow the de Gennes factor along the lanthanide series. Neutron diffraction shows for the Tb- and Ho-compounds that strongly ferromagnetic structures characterized by a k = 0 magnetic propagation vector are formed on two different rare earth sublattices which are canted to each other. Only in the Tb-containing phases the magnetic transition leads to a symmetry reduction from tetragonal I41/amd to at least monoclinic I2/a. Magnetic symmetry analysis is used to argue that the presence of a magnetic moment component along the original tetragonal axis should be at the origin of this magneto-structural transition in the Tb-compounds with a possible further symmetry lowering.

Phase transitions and the magnetocaloric effect in (Gd,Tb)5Si2Ge2 compounds doped with Ti

We have conducted the study of structural, magnetic, magnetothermal, and magnetoelastic properties of four rare-earth compounds: Gd4.5Tb0.5Si2Ge2, Gd4TbSi2Ge2, Gd4.4Tb0.5Ti0.1Si2Ge2, and Gd3.9TbTi0.1Si2Ge2 in the vicinity of magnetically induced phase transitions. We demonstrate that the introduction of Ti into the rare-earth sublattice separates the structural and magnetic phase transitions and changes the order of magnetic phase transition from type I to II, while preserving high values of magnetocaloric effect (MCE). Additionally, incorporating a small quantity of Tb enables the creation of compounds with enhanced MCE values over a specific temperature range of 240–290 K. The observed phenomena can be attributed to the combined effects of forced magnetization and alteration of magnetic susceptibility during the structural phase transition that accompany the magnetic phase changes in these compounds.

Rare Earth Based Iron Garnet – A Survey on Its Magnetic Properties

Garnet is a well-known material for a long-time by the scientific community but still today scientists are focusing on it due to the rapid application-based development of this material. When rare earth iron garnets (REIG) are formed by substituting the rare-earth ions with unfilled 4fn orbitals, the magnetic properties of the iron garnets exhibit an interesting characteristic. For rare earth elements, the 4f electrons are shielded from the crystal field as these are surrounded by 5s, 5p, or 5d orbitals. That is why the exchange field between rare earth ions is much smaller than that between iron-iron and rare earth-iron. The magnetic moment of REIG will be both due to the orbital and spin moment. The magnetization of REIG at different temperatures (T) is due to the dominant contribution of different sublattices. At high and low T, the dominant sublattices are iron and rare earth sublattices respectively. The magnetic and non-magnetic ion substitution in REIG also play a very important role in deciding their magnetic property. In this review, we have tried to figure out the basic underlying physics behind the origin of remarkable magnetic behavior in REIG.

Exchange coupling due to spin-imbalance in Er magnetic sublattice within Er/Tb multilayers

Topologically stable spin spiral structures in rare-earth (RE) can form the basis of realizing all-spin-based technology as strong exchange coupling has been reported earlier at the ferromagnet (FM)–RE or RE–RE interfaces around the temperature range where both layers are essentially ferromagnetic. Owing to the small number of irreversible spins in the non-collinear configuration within the RE layer, very weak coupling is rendered around the temperature range of the helical phase. Competing anisotropies in Er result in a conical c-axis ferromagnetic structure below 20 K while Tb orders ferromagnetically with an easy axis along the a-axis below 221 K. Here, we grow heteroepitaxial Er/Tb multilayers and find an exchange coupling of up to +170±10 Oe, particularly below 20 K. This exchange bias phenomenon can be due to the effect of spin spiral to conical phase fraction within Er below 20 K. Additionally, we find inter-domain magnetic AC frequency-responsive magnetic interaction behavior which does not comply with the spin-freezing/blocking like ordering around the crossover range of helical to conical phase. Empirically, this can be explained in terms of the increased spin-imbalance in each Er magnetic sublattice due to the atomic disorder induced during the field cooling process. This unconventional exchange coupling could essentially enable us to tailor non-collinear spintronic devices in the future with induced spin-imbalance in the RE sublattice.

SIGN-REVERSING MAGNETOCALORIC EFFECT IN R2Fe10Al7 (R = Dy AND Ho) COMPOUNDS

The magnetic properties of rare-earth ferrimagnetic compounds Dy2Fe10Al7 and Ho2Fe10Al7 with a Th2Zn17 crystal structure have been studied. The temperature dependences of the magnetization and magnetocaloric effect have been examined in the temperature range of 4.2‒300 K in magnetic fields of up to 70 and 18 kOe, respectively. The temperatures of magnetic compensation of the magnetization of the rareearth and iron sublattices have been determined. The magnetocaloric effect has been determined by the direct method. It has been found that the sign of the effect changes near the magnetic compensation point. This phenomenon has an application potential.

Structures and room-temperature magnetic properties of entropy-modulated Gd<sub>2</sub>Co<sub>17</sub> based intermetallic compounds

<sec>The entropy-modulated material has been a hot topic due to its unique design concept and excellent properties. However, previous studies of entropy-modulated materials mainly focused on the alloys with simple face-centered cubic, or body-centered cubic, or hexagonal close-packed structures. In this work, the design concept of entropy-modulation is introduced into Gd<sub>2</sub>Co<sub>17</sub> based intermetallic compound, and the effect of high configuration entropy on the structural stabilization and room-temperature magnetic properties of Gd<sub>2</sub>Co<sub>17</sub> based intermetallic compound are studied systematically.</sec><sec>The samples are prepared by vacuum Arc melting technology in an ultrahigh-purity Ar atmosphere and followed by annealing at 1000 ℃ for 8 days and finally by quenching in cool water. The fine powders are prepared by grinding the ingots in an agate mortar. The powder XRD and SEM-EDS are used to check the crystal structures and chemical compositions. To study the magnetic properties, the column-like samples are prepared by mixing the fine powder and epoxy with a weight ratio of 1∶1, and then aligned under an applied field of 1 T at room temperature.</sec><sec>The high configuration entropy is found to play an important role in the structural stabilization and magnetic properties of Gd<sub>2</sub>Co<sub>17</sub> based medium- and high-entropy intermetallic compounds. The XRD patterns and Rietveld structural refinement results confirm that all the samples are single-phase. The structure depends on the effective atomic radius <i>R</i><sub><i>A</i></sub>, the structure of entropized Gd<sub>2</sub>Co<sub>17</sub> based intermetallics can be stabilized into rhombohedral Th<sub>2</sub>Zn<sub>17</sub>-type with <i>R</i><sub>A </sub>> 1.416 or hexagonal Th<sub>2</sub>Ni<sub>17</sub>-type with <i>R</i><sub>A<i> </i></sub>< 1.4105. According to thermodynamic calculations of entropized Gd<sub>2</sub>Co<sub>17</sub> intermeatllics, the atomic radius difference Δ<i>r</i> ranges from 0.55% to 1.81%, and the mixing enthalpy <inline-formula><tex-math id="M3">\begin{document}$ \Delta {{\boldsymbol{H}}}_{{\rm{m}}{\rm{i}}{\rm{x}}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20221995_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20221995_M3.png"/></alternatives></inline-formula> is corresponding to 0 for the rare earth site, –4 to –1 kJ/mol for the transition metal site, and –8.54 to –5.13 kJ/mol between rare earth and transition metal sites. It is suggested that all the thermodynamic parameters meet the criteria for the formation of single-phase medium- and high-entropy intermetallic compounds. The configuration entropy changes from 0.69R to 1.39R. The room temperature magnetic properties are significantly improved by the modulation of entropized design at rare earth and transition metal sublattices. The entropization enhances the saturation moments of all samples, which can be explained with a modified magnetic valence model. The value of <inline-formula><tex-math id="M4">\begin{document}${N}_{{\rm{sp}}}^{\uparrow }$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20221995_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20221995_M4.png"/></alternatives></inline-formula> (the number of the electrons in the unpolarized sp conduction bands) increases from 0.3 to 0.4 after entropization, the indirect interaction between rare earth and transition metal sublattice is increased, the spin moment of s conducting electron as a medium of two sublattices is enhanced, and the magnetic moment is increased. The entropization also induces magnetic anisotropy to transform from basal plane to easy axis for the entropized design at transition metal sublattice and the coercivity of rare earth to increase.</sec>

Electronic and magnetic properties of intermetallic kagome magnets RV6Sn6(R=Tb−Tm)

We present a systematic study of the structure, electronic, and magnetic properties of a new branch of intermetalllic compounds, $R$V$_6$Sn$_6$ ($R$ = Tb - Tm) by using X-ray diffraction, magnetic susceptibility, magnetization, electrical transport, and heat-capacity measurements. These compounds feature a combination of a non-magnetic vanadium kagome sublattice and a magnetic rare-earth triangular sublattice that supports various spin anisotropies based on different $R$ ions. We find magnetic orders for the $R$ = Tb, Dy, and Ho compounds at 4.4, 3, 2.5 K, respectively, while no ordering is detected down to 0.4 K for the $R$ = Er and Tm compounds with easy-plane anisotropies. Electronically, we found no superconductivity or charge ordering transition down to 0.4 K for any member of this family, while all compounds exhibit multi-band transport properties that originate from the band topology of the vanadium kagome sublattice.

Observation of spin-glass-like characteristics in ferrimagnetic TbCo through energy-level-selective approach

Rare earth (RE)–transition metal (TM) ferrimagnetic alloys are gaining increasing attention because of their potential use in the field of antiferromagnetic spintronics. The moment from RE sub-lattice primarily originates from the 4f-electrons located far below the Fermi level (EF), and the moment from TM sub-lattice arises from the 3d-electrons across the EF. Therefore, the individual magnetic moment configurations at different energy levels must be explored to clarify the microscopic mechanism of antiferromagnetic spin dynamics. Considering these issues, here we investigate the energy-level-selective magnetic moment configuration in ferrimagnetic TbCo alloy. We reveal that magnetic moments at deeper energy levels are more easily altered by the external magnetic field than those near the EF. More importantly, we find that the magnetic moments at deeper energy levels exhibit a spin-glass-like characteristics such as slow dynamics and magnetic moment freezing whereas those at EF do not. These unique energy-level-dependent characteristics of RE-TM ferrimagnet may provide a better understanding of ferrimagnet, which could be useful in spintronic applications as well as in spin-glass studies.

Cocktail effect on RT5-type (R = rare earth, T = 3d transition metal) high entropy intermetallic compounds

The alloys with normal compositions of (Sm1/2Ce1/2)(Co1/3Cu1/3Ni1/3)5, (Sm1/2Pr1/2)(Co1/3Cu1/3Ni1/3)5, (Sm1/2Nd1/2)(Co1/3Cu1/3Ni1/3)5, (Sm1/3Ce1/3Pr1/3)(Co1/3Cu1/3Ni1/3)5, and (Sm1/3Ce1/3Nd1/3)(Co1/3Cu1/3 Ni1/3)5 are designed by mixing RCo5, RNi5, and RCu5 for studying their cocktail effects. These designed alloys are prepared by vacuum Arc melting technology. Their single-phase characteristics are experimentally confirmed by X-ray diffraction and scanning electron microscope with energy dispersive spectrum, and also theoretically confirmed by the reported single-phase formation rule of high entropy alloys: atomic radius difference within 6%, nonpositive mixing enthalpy, and high configuration entropy above 1.50R. The designed alloys are suggested to be the high entropy intermetallic compounds due to their single-phase characteristics and high configuration entropy. The magnetic cocktail effect is observed in magnetic measurements. These intermetallic compounds show low-temperature magnetic transition and field-induced ferromagnetic characteristics. The cocktail effect is suggested to be modulated by the spins with random directions at rare earth and transition metal sublattices caused by mixture of the multiple individual RCo5, RNi5, and RCu5 intermetallic compounds.

Asynchronous current-induced switching of rare-earth and transition-metal sublattices in ferrimagnetic alloys.

Ferrimagnetic alloys are model systems for understanding the ultrafast magnetization switching in materials with antiferromagnetically coupled sublattices. Here we investigate the dynamics of the rare-earth and transition-metal sublattices in ferrimagnetic GdFeCo and TbCo dots excited by spin-orbit torques with combined temporal, spatial and elemental resolution. We observe distinct switching regimes in which the magnetizations of the two sublattices either remain synchronized throughout the reversal process or switch following different trajectories in time and space. In the latter case, we observe a transient ferromagnetic state that lasts up to 2 ns. The asynchronous switching of the two magnetizations is ascribed to the master-agent dynamics induced by the spin-orbit torques on the transition-metal and rare-earth sublattices and their weak antiferromagnetic coupling, which depends sensitively on the alloy microstructure. Larger antiferromagnetic exchange leads to faster switching and shorter recovery of the magnetization after a current pulse. Our findings provide insight into the dynamics of ferrimagnets and the design of spintronic devices with fast and uniform switching.

The magnetic structure of DyFeO3 revisited: Fe spin reorientation and Dy incommensurate magnetic order

High resolution and high intensity neutron powder diffraction is used to study the ground state magnetic order and the spin reorientation transition in the orthoferrite DyFeO3. The transition from the high temperature k = 0 Γ4 (G x A y F z ) to the low temperature Γ1 (A x G y C z ) type order of the Fe-sublattice is found at T SR = 73 K and does not show any thermal hysteresis. Below T N2 = 4 K the Dy-sublattice orders in an incommensurate magnetic structure with k = [0, 0, 0.028] while the Fe-sublattice keeps its commensurate Γ1 type order. DyFeO3 is the first orthoferrite RFeO3 to possess an incommensurate magnetic order of the rare earth sublattice under zero field conditions; an important piece of information neglected in the recent discussion of its multiferroic properties.

Spin-glass behavior and magnetocaloric properties of high-entropy perovskite oxides

The high-entropy concept has been recently proposed to be a promising paradigm to enhance the magnetocaloric properties of materials. Motivated by this, the magnetic properties and the magnetocaloric performance of two high-entropy perovskites (Dy1/4Ho1/4Er1/4Tb1/4)FeO3 and (Gd1/5Dy1/5Ho1/5Er1/5Tb1/5)FeO3 have been investigated. The magnetic measurements indicate that a spin-glass phase occurs at low temperatures in the high-entropy compounds, which is induced by the strong compositional disorder of rare-earth sublattice. The glassy state can lead to a sluggish magnetic transition and consequently a potential improvement in the magnetocaloric performance. Due to the increase in configurational entropy, large refrigerant capacity of 247 and 203 J/kg for a magnetic field change of 70 kOe is obtained in the (Gd1/5Dy1/5Ho1/5Er1/5Tb1/5)FeO3 and (Dy1/4Ho1/4Er1/4Tb1/4)FeO3 compounds, respectively. Our findings highlight the availability of spin order control through tuning the configurational entropy and demonstrate the key role of high-entropy design in enhancing the magnetocaloric properties of materials.

Symmetry Analysis of Magnetoelectric Effects in Perovskite-Based Multiferroics.

In this article, we performed symmetry analysis of perovskite-based multiferroics: bismuth ferrite (BiFeO3)-like, orthochromites (RCrO3), and Ruddlesden–Popper perovskites (Ca3Mn2O7-like), being the typical representatives of multiferroics of the trigonal, orthorhombic, and tetragonal crystal families, and we explored the effect of crystallographic distortions on magnetoelectric properties. We determined the principal order parameters for each of the considered structures and obtained their invariant combinations consistent with the particular symmetry. This approach allowed us to analyze the features of the magnetoelectric effect observed during structural phase transitions in BixR1−xFeO3 compounds and to show that the rare-earth sublattice has an impact on the linear magnetoelectric effect allowed by the symmetry of the new structure. It was shown that the magnetoelectric properties of orthochromites are attributed to the couplings between the magnetic and electric dipole moments arising near Cr3+ ions due to distortions linked with rotations and deformations of the CrO6 octahedra. For the first time, such a symmetry consideration was implemented in the analysis of the Ruddlesden–Popper structures, which demonstrates the possibility of realizing the magnetoelectric effect in the Ruddlesden–Popper phases containing magnetically active cations, and allows the estimation of the conditions required for its optimization.

Magnetic and magnetocaloric properties of Ho-=SUB=-1-x-=/SUB=-Y-=SUB=-x-=/SUB=-(Co-=SUB=-0.84-=/SUB=-Fe-=SUB=-0.16-=/SUB=-)-=SUB=-2-=/SUB=- compounds

Crystal structure, temperature and field dependences of magnetization, high-field susceptibility, and magnetocaloric effect (MCE) of Ho1-xYx(Co0.84Fe0.16)2 polycrystalline compounds (x=0-1) in magnetic fields up to 90 kOe in a temperature range of 5-400 K are investigated. An analysis of temperature dependences of magnetization (sigma) showed that, depending on the yttrium content (x), up to three "critical" temperatures can be simultaneously present in the studied samples: spin-reorientation (Tsr), magnetic compensation point (Tcomp), and Curie temperature (TC). The temperature dependence of the high-field susceptibility (chihf) of all samples with x<1 has an extremum in the vicinity of 100 K, where a significant MCE is observed, associated with a sharp change in the magnetization of the rare-earth sublattice. The temperature dependences of the magnetic entropy change (Delta Sm) and the adiabatic temperature change (Delta Tad) have a complex shape and reflect all the above-mentioned "critical" temperatures observed at different x. Keywords: magnetic properties, direct and inverse magnetocaloric effect, adiabatic temperature change, magnetic moment, Laves phases, Curie temperature, compensation point, spin-reorientation transition.

Néel ordering in the distorted honeycomb pyrosilicate: C–Er2Si2O7

The rare-earth pyrosilicate family of compounds (RE2Si2O7) hosts a variety of polymorphs, some with honeycomb-like geometries of the rare-earth sublattices, and the magnetism has yet to be deeply explored in many of the cases. Here we report on the ground state properties of C–Er2Si2O7. C–Er2Si2O7 crystallizes in the C2/m space group and the Er3+ atoms form a distorted honeycomb lattice in the a–b plane. We have utilized specific heat, DC susceptibility, and neutron diffraction measurements to characterize C–Er2Si2O7. Our specific heat and DC susceptibility measurements show signatures of antiferromagnetic ordering at 2.3 K. Neutron powder diffraction confirms this transition temperature and the relative intensities of the magnetic Bragg peaks are consistent with a collinear Néel state in the magnetic space group C2’/m, with ordered moment of 6.61 μ B canted 13° away from the c-axis toward the a-axis. These results are discussed in relation to the isostructural quantum dimer magnet compound Yb2Si2O7.