Spin Reorientation Temperature TSR Research Articles

Intrinsic magnetism and practical potential of 2:14:1-type magnet with rare earth supplied only by misch-metal

2:14:1-type rare earth (R) permanent magnet R2Fe14B, as a functional material, plays an indispensable role in transportation, machinery, energy and other fields. Under the pressure of resources, cost and environment, special attention has been devoted to magnets replaced by high-abundance rare earth. But until now, 2:14:1 phase containing only misch-metal (MM) is not considered suitable for practical production. In this work, from the perspective of intrinsic properties, it is confirmed for the first time that MM2Fe14B with MM (La, Ce and other high-abundance rare earth content as high as 80%) has the potential to become a permanent material. The saturation magnetization Ms at 300 K is 27.36 μB/f.u, and the anisotropy parameters are μ0Ha = 4.2 T, K1 = 1.39 MJ/m3 and K2 = 0.42 MJ/m3. We noted that the temperature dependence of Ms, K1 and K2 are very similar to Nd2Fe14B. Curie temperature TC and spin reorientation temperature Tsr of MM2Fe14B are 488 K and 74 K, respectively. When the temperature is lower than Tsr, the anisotropy changes from easy-uniaxial to easy-cone. The spin reorientation angle θs is about 18° at 4.2 K, less than Nd2Fe14B. Small θs means that strong uniaxial anisotropy can be maintained, which is important to achieve high-performance. Micromagnetic simulation was also introduced to confirm the effect of θs and grain boundary on MM-Fe-B performance. The intrinsic magnetism not only provides strong evidence for the practicability of MM-Fe-B, but also of great significance for further study on the mechanism of rare earth magnets with high-performance and high-abundance.

Near room temperature hexagonal multiferroic (Yb0.25Lu0.25In0.25Sc0.25)FeO3 high-entropy ceramics

In this work, h-RFeO3 multiferroic high-entropy ceramics are designed by introducing high-entropy concept with four elements (Yb, Lu, In, Sc) for R site. (Yb0.25Lu0.25In0.25Sc0.25)FeO3 high-entropy ceramics are prepared by the standard solid-state reaction methods. The samples prepared with precursors were identified to crystalize in the pure hexagonal structure with polar space group (P63cm) at room temperature. By the analysis of the variable XRD patterns, it is speculated that the ferroelectric transition temperature of the sample is above 773 K. Meanwhile, three magnetic anomalies are determined for high-entropy ceramics, which is the antiferromagnetic transition at Néel temperature TÑ280 K, the spin-reorientation temperature TSR∼145 K and the reasonable ferromagnetic-like clusters without long ordering in TN < T < TA (∼397 K). Besides, it is observed that the peak intensity of the pyroelectric current around TN can be tuned by magnetic field, which is indicated the magnetoelectric coupling effect in (Yb0.25Lu0.25In0.25Sc0.25)FeO3 high-entropy ceramics. These results indicate the ferroelectric and antiferromagnetic orders are coexist in the h-RFeO3 high-entropy ceramics as promising near room temperature multiferroic materials, and it is an effective way to obtain a new type single-phase multiferroic materials.

Structural and magnetic properties of DyCrO3

In this contribution, the structural and magnetic properties of DyCrO3 are studied, along with the magnetocaloric effect in this compound. The susceptibility as a function of temperature, χ(T), indicates that DyCrO3 has a G-type antiferromagnetic behaviour with weak ferromagnetism below Néel temperature, TNCr, at 147.1 ± 0.1 K, attributed to the ordering of Cr moments. The Dy moments orders antiferromagnetically below the spin reorientation temperature TSR = 4.81 ± 0.04 K. The dependence of magnetization on the applied magnetic field, Mμ0H, shows a behaviour that corresponds to the χ(T) data. Arrott plots reflect the various magnetic orderings with a change in the gradient of the curves. For the first time, the magnetocaloric effect of sol-gel synthesized DyCrO3 is studied having an average particle size 215 ± 3 nm as obtained from transmission electron microscopy (TEM). Large magnetocaloric effects (MCE) are observed in the temperature range of 10 to 80 K for DyCrO3. The compound shows a relatively large magnetic entropy change (ΔSM) of 21 J.Kg−1.K−1 and relative cooling power (RCP) of 498 J.Kg−1 at 7 T and 10 K. Assuming the relations |ΔSmT,H|=a(H)n and RCP=CH1+1δ, with critical exponents n = 1 and δ → ∞ were obtained from the linearization, confirming the weak ferromagnetic behaviour.

Tunable structural and magnetic properties of NiAs-type MnxSb (1.00[formula omitted]x[formula omitted]1.30) compounds

Mn-based alloys can exhibit a variety of magnetic properties related to their tunable exchange interactions. In this work, structural and magnetic properties of hexagonal NiAs-type MnxSb (1.00≤x≤1.30) compounds are studied with a combination of X-ray diffraction, neutron diffraction, and magnetic measurements. It is found that the magnetization, Curie temperature, and magnetocrystalline anisotropy of MnxSb compounds can be tuned by controlling Mn concentration and doping at interstitial (2d) sites. With increasing Mn concentration, magnetic moments of Mn atoms decrease and deviate gradually from the ab-plane to the c-axis for 1.20≤x≤1.22 at room temperature, which leads to a decrease of the Curie temperature Tc and the spin reorientation temperature TSR. By doping with nonmagnetic elements, a substantial room-temperature magnetocaloric effect without magnetic hysteresis was achieved for Mn1.12Zr0.1Sb compound, which is highly beneficial to the practical magnetic refrigeration application.

Structural transition and magnetic properties of high Cr-doped BiFeO3 ceramic

Abstract Magnetic properties of BiFe1-xCrxO3 perovskite-type solids reaction synthesized at high pressure were investigated and a magnetic phase diagram was established. X-ray diffraction data revealed a crystal structure transformation from rhombohedral to monoclinic as Cr3+ ions substituted Fe ions in the samples. Néel temperature TN and spin-reorientation temperature TSR were determined from dM/dT by measuring the temperature dependence of magnetization (M-T). The magnetization results indicated that TN and TSR were strongly dependent on Cr3+ ion doping; both TN and TSR decreased with the increase of Cr3+ doping. The magnetic hysteresis loops investigated at room temperature reflected an antiferromagnetic behavior from x= 0.4 to 0.6 and weak ferromagnetic at x=1.0. Besides, the remnant magnetization Mr and maximum magnetization Mmax increased with increasing x from 0.4 up to 1.0. The Cr doping was found to be helpful in reducing coercivity Hc for the magnetic samples from x= 0.4 to 0.8 and their applications as magnetic sensors are possible.

All Electrical Access to Topological Transport Features in Mn1.8PtSn Films.

The presence of nontrivial magnetic topology can give rise to nonvanishing scalar spin chirality and consequently a topological Hall or Nernst effect. In turn, topological transport signals can serve as indicators for topological spin structures. This is particularly important in thin films or nanopatterned materials where the spin structure is not readily accessible. Conventionally, the topological response is determined by combining magnetotransport data with an independent magnetometry experiment. This approach is prone to introduce measurement artifacts. In this study, we report the observation of large topological Hall and Nernst effects in micropatterned thin films of Mn1.8PtSn below the spin reorientation temperature TSR ≈ 190 K. The magnitude of the topological Hall effect ρ xyT = 8 nΩm is close to the value reported in bulk Mn2PtSn, and the topological Nernst effect S xyT = 115 nV K-1 measured in the same microstructure has a similar magnitude as reported for bulk MnGe ( S xyT ∼ 150 nV K-1), the only other material where a topological Nernst was reported. We use our data as a model system to introduce a topological quantity, which allows one to detect the presence of topological transport effects without the need for independent magnetometry data. Our approach thus enables the study of topological transport also in nanopatterned materials without detrimental magnetization related limitations.

Influences of element segregation on the magnetic properties in nanocrystalline Nd-Ce-Fe-B alloys

The RE-rich (Ce1−xNdx)16Fe78B6 (x = 0–1) nanocrystalline alloys were prepared by melt-spinning method. The transmission electron microscopy equipped with EDS was employed to investigate the microstructure and rare-earth element segregation. The average Nd/RE ratios in 2:14:1 grains are 22, 52, 67, 74, 78, and 81% for the x = 0.1, 0.4, 0.5, 0.6, 0.7, and 0.8 alloys, respectively, which are larger than the nominal ratios, indicating a Nd segregation in 2:14:1 phase. The Nd/RE ratio changing with x shows a two-stage of increment: the average increment in x = 0.1–0.5 alloys is much higher than that of x = 0.5–0.8 alloys. The corresponding change is also observed in the plotted intrinsic parameters of cell volume V, hyperfine field Bhf, and spin reorientation temperature TSR of the 2:14:1 phase changing with x curves. The high Ce-contained RE-rich Nd-Ce-Fe-B with strong element segregation shows high coercivities and high performance/price ratio. The present results thus contribute to understanding the fundamental mechanism of Ce-contained Nd-Ce-Fe-B permanent magnets and taking advantage of the element segregation.

Pressure dependence of the magnetic properties and phase diagram of HoCo12B6 ferrimagnetic compound

Abstract The magnetic properties of HoCo12B6 ferrimagnetic compound are investigated versus the magnetic field, temperature and pressure. The magnetic phase diagram exhibits three remarkable temperatures: the ordering temperature TC, the spin reorientation temperature TSR and the compensation temperature TCOMP at 147 K, 76 K and 47 K respectively. In HoCo12B6 intermetallic system the spontaneous magnetization resulting from the antiparallel coupling of the magnetic moments of Ho and Co sublattices is pressure insensitive at lowest temperatures whereas it decreases with pressure at temperature range above TSR. The mean Co magnetic moment is small (

Hydrostatic pressure modulated spin-reorientation transition and magnetocaloric effect in PrGa compound

The effect of hydrostatic pressure on the spin-reorientation transition and magnetocaloric effect in PrGa compound has been experimentally investigated. Because of the significant change of lattice parameter along with the spin reorientation, hydrostatic pressure can largely shift the spin reorientation temperature TSR from 28 K down to 16 K under 1.14 GPa, while magnetic transition at TC∼37 K hardly changes. Although the maximum entropy change ΔSM for a magnetic field change of 0–5T decreases from 9.2 J/kg K to 5.8 J/kg K as a pressure of 1.14 GPa was applied, an asymmetric broadening of ΔSM with magnetic field occurs due to the widening of metamagnetic transition window caused by pressure. As a result, a plateau develops on the ΔSM-T curve, and 10% improvement of effective refrigerant capacity RCeff has been achieved. The origin can be ascribed to the significant impact of the pressure on the lattice and crystal field interaction, which not only strengthens the first-order nature of the spin reorientation transition but also enlarges the distance between TSR and TC and broadens the temperature window of metamagnetic transition involving the specific spin alignment. The tunable TSR and enhanced RCeff by pressure in PrGa demonstrate that the compound can be useful in developing multi-field driven refrigeration technique.

High performance misch-metal (MM)-Fe-B magnets prepared by melt spinning

A series of misch-metal (MM = 28.27 wt % La, 50.46 wt % Ce, 5.22 wt % Pr, 15.66 wt % Nd)-iron-boron isotropic ribbons with atomic formula (MM)12+xFe82-x-yB6+y (x = 0, 1, 2, 3, 4, y = 0, 0.5, 1, 1.5, 2) are prepared by melt spinning technique. A large energy product (BH)max of 12 MGOe is obtained with the composition of MM13Fe81B6 at optimized processing. The ribbons with both coercivity larger than 10 kOe and (BH)max larger than 10 MGOe are achieved in a wide composition range. All the samples exhibit the tetragonal crystal structure. The magnetization and Henkel plot (δM) measurements indicate that the ribbons have a relatively homogeneous microstructure and strong exchange-coupling interactions. The average grain size of the ribbons is around 30 nm determined via Scherrer's formula. Meanwhile, the transmission electron microscope (TEM) image also verifies that the ribbons have a homogeneous nanoscale microstructure. In addition, the spin reorientation temperature Tsr is investigated by ac susceptibility χac measurement.

Investigation of the magnetic properties of Dy doped Nd-Fe-B permanent magnet by using Mössbauer spectroscopy

The crystal and the magnetic properties of (Nd35.00-x Dy x )Fe bal.Cu0.15Co1.50Al0.20Nb0.35B1.00 (wt.%; x = 3.50, 6.00, and 8.00) samples are investigated by using x-ray diffractometer (XRD), vibrating smple magnetometer (VSM), and Mossbauer spectrometer. The crystal structure is determined to be tetragonal with the P42/mnm space group. The saturation magnetization (M s ) decreases while the coercivity (H c ) increases with increasing Dy ion concentration. Based on the zero-filed-cooled (ZFC) curves, all the samples show spin reorientation, and the spin-reorientation temperature TSR decreases with increasing Dy ion concentration. The Mossbauer spectra measured at 295 K show decreasing with increasing Dy concentration, and the abrupt changes both in the magnetic hyperfine field (H hf ) and the electric quadrupole shift (E Q) at temperatures around T SR .

Magnetocrystalline anisotropy of magnetite

The spin reorientation temperature TSR of stoichiometric Fe3O4, as well as of magnetite with a small number of vacancies and magnetite containing a low concentration of Ti, Zn, Al and Ga was measured on single-crystal samples using the ac susceptibility. In the same experiment the temperature TV of the Verwey transition was also found. The results show that a correlation between TSR and TV exists. The electronic structure of the compounds studied was determined using the density-functional-based GGA + U method. For stoichiometric magnetite the first and second cubic anisotropy constants were calculated, while for magnetite with defects the distribution of electron density using the ‘atoms in molecules’ approach was determined. Based on a combination of experimental results with the electronic structure calculations an explanation of the temperature dependence of the magnetocrystalline anisotropy of magnetite is suggested.

Structural and Magnetic Properties of ${\hbox {Tm}}_{2}{\hbox {CrFe}}_{16-x}{\hbox {Si}}_{x}$ Compounds

The structural and magnetic properties of Tm <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> CrFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16-x</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> =0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0) compounds are investigated by means of X-ray diffraction and magnetization measurements. The results show that the Tm <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> CrFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16-x</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> compounds are in a single phase with the hexagonal Th <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Ni <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sub> -type structure. The lattice parameters <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> and the unit-cell volume <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> decrease monotonously with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> increasing. The Curie temperature <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> increases initially ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> <; 1.5) with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> increasing, followed by a decrease at higher concentrations ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> >; 1.5) . There is a maximum of the Curie temperature, which is about 450 K, at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> =1.5. Spin reorientations are observed in the temperature dependences of the magnetization of Tm <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> CrFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16-x</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> compounds. The spin reorientation temperature ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sr</sub> ) increases from 144 K at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> =0 to 259 K at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> =3.0 with <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> increasing. This means that the Si atoms substituting for Fe atoms can increase obviously the easy-axis magnetocrystalline anisotropy. The analysis shows that the effect of Cr substitution and the effect of Si substitution on the Curie temperature and the magnetocrystalline anisotropy of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">17</sub> compound can be superposed.

Effect of additive elements on exchange coupling and spin reorientation transition of nanocrystalline single-phase Nd-Fe-B alloy

Nd12.3Fe81.7−xZrxB6.0 (x=0, 1.5) and (NdDyTb)12.3(FeZrNbCu)81.7−yCoyB6.0 (y=0, 12) ribbons were prepared by melt spinning at 22 m/s and subsequent annealing. The influences of Zr, Dy/Tb and Co substitutions on magnetic properties and spin reorientation transitions of nanophase Nd2Fe14B have been systematically investigated. Compared with Zr-free sample, the remanence, intrinsic coercivity and maximum energy product for Nd12.3Fe80.2Zr1.5B6.0 ribbon increase by 10.8 %, 17.8 % and 60.2 %, respectively. The significant improvement of magnetic properties originates from the finer grains of the sample by introducing Zr, which leads to the stronger exchange coupling between neighboring grains. The intrinsic coercivity for (DyTb)-substituted ribbon is significantly increased although the remanence is reduced, which could be compensated by the substitution of Co for Fe. The spin reorientation temperature Tsr of nanocrystalline Nd2Fe14B alloys was determined by measuring the ac magnetic susceptibility. It was found to be lower than that of bulk Nd2Fe14B. The substitutions of Zr, Dy/Tb and Co result in reduction of Tsr. The smaller the grain size, the lower the Tsr will be. Influence of spin reorientation on magnetization characteristics of nanophase Nd2Fe14B was discussed.

Magnetic and structural phase transitions of MnBi under high magnetic fields

High-field x-ray diffraction and magnetization measurements and differential thermal analysis (DTA) were carried out for polycrystalline MnBi with an NiAs-type hexagonal structure to investigate its magnetic and structural phase transitions. The lattice parameter a rapidly decreases below the spin reorientation temperature TSR(=90 K) in a zero magnetic field. The parameter c decreases gradually with decreasing temperature and exhibits an anomaly in the vicinity of TSR. By applying a magnetic field of 5 T, the parameter a increases by ∼0.05% when T<TSR and varies smoothly when 8≤T≤300 K. DTA data show that the magnetic phase transition temperature from the ferromagnetic state to the paramagnetic state increases linearly at a rate of 2 KT−1 with increasing magnetic field up to 14 T.

Spin configuration and magnetostrictive properties of Laves compounds TbxDy0.7−xPr0.3(Fe0.9B0.1)1.93(0.10⩽x⩽0.28)

The spin configuration and magnetostrictive properties of TbxDy0.7−xPr0.3(Fe0.9B0.1)1.93 (0.10⩽x⩽0.28) Laves compounds are investigated. The spin phase diagram for the compounds is constructed to illustrate both the composition dependence of the Curie point TC and spin reorientation temperature TSR and the arrangement for the easy magnetization direction (EMD). It is found that when x is increased from 0.16 to 0.28, TC increases from 617to623K, while TSR decreases from 375to160K at which the EMD reorients from ⟨100⟩ to ⟨111⟩ axis. The magnetization and magnetostriction of the compounds are measured as a function of applied field. The magnetocrystalline anisotropy constant K1 and the ratio λa∕K1 reach a minimum and a maximum value at x=0.22, respectively. The single phase Tb0.22Dy0.48Pr0.3(Fe0.9B0.1)1.93 compound has the lowest magnetocrystalline anisotropy, the highest magnetostriction to anisotropy ratio, and a large spontaneous magnetostriction λ111 of ∼1500ppm at room temperature. In view of these properties, the compound is a promising magnetostrictive material.

Structure and magnetic properties of (Nd1－xErx)3Fe25Cr4.0 compounds

Structure and magnetic properties of the (Nd1-xErx)3Fe25Cr40 (x=0—10) compounds have been investigated by means of x -ray diffraction and magnetic measurements. It is found that the compounds with x =0—08 crystallize in Nd3(Fe,Ti)29-type structure, A 2/m space grou p, but those with 082Ni17-type structure, P63/mmc space group. Both the Curie tem perat ure Tc and the saturation magnetization Ms of (Nd1 -xErx)3Fe25Cr40 de crease monotonically with increasing Er content. The easy magne tization direction (EMD) of the Nd3Fe25Cr40 compound is close to the ［040］ direction at room temperature, but makes a tilted angle with the ba sal plane of 1∶5 structure. With increasing Er content the EMD changes to much close to the [402] direction and the tilted angle increases. AC susceptibility m easurement indicates the appearance of a spin reorientation at low temperatures for the compounds with x=0—04 and x=10, and the spin reorientation temperature Tsr increases monotonically as the Er content increas es fo r the compounds with x=0—04 First-order magnetization process (FOMP) is observed in the compounds with 0≤x≤08 and the critical field Bc rof the FOMP decreases with increasing Er content from 66T for x=0 to 20T for x=07

Formation, structure and magnetic properties of Nd3Fe26.8−xCoxV2.2 compounds

Single-phase Nd3Fe26.8−xCoxV2.2 compounds with Nd3(Fe,Ti)29-type structure have been synthesized successfully for x = 0–12; and their structures and magnetic properties were investigated by x-ray diffraction and magnetic measurements. The Curie temperature increases drastically with increasing Co content from 500 K for x = 0–847 K for x = 12. All the compounds show a spin reorientation transition as temperature decreases. Spin reorientation temperature Tsr shows an increasing tendency with the exception of a minimum at around x = 6. Saturation magnetization increases monotonically with increasing Co content, which can be understood in terms of a rigid band model. The anisotropy field at 5 K decreases with increasing Co content. All the compounds show easy-plane-type anisotropy at room temperature and the series of the compounds is not suitable for permanent materials.

Structure and magnetic properties of (Nd1−xErx)3Fe18Co6Cr5 (x = 0.0–0.8) compounds

The structure and magnetic properties of the (Nd1−xErx)3Fe18Co6Cr5 compounds with x = 0.0–0.8 have been investigated by means of x-ray diffraction and magnetic measurements. It is found that all the compounds are single phase and crystallize in the Nd3(Fe,Ti)29-type structure with monoclinic symmetry and space group A2/m. The lattice constants a, b and c and the unit-cell volume V show a tendency to decrease with increasing Er content, reflecting the lanthanide contraction. The Curie temperature decreases with increasing Er content. The spin-reorientation temperature Tsr increases with increasing Er content till x = 0.2, then tends to saturate upon further increase in Er content. The saturation magnetization at 5 K decreases with increasing Er content owing to the antiferromagnetic coupling between Er and Nd moments. A first-order magnetization process is observed for compounds with x = 0, 0.2 and 0.4 at critical field values of 8 T, 4.5 T and 3.5 T, respectively, applied along the hard magnetization direction.

Structural and magnetic properties of R(Fe1−yCoy)12−xNbx compounds

The magnetic properties of RFe12−xNbx and R(Fe1−yCoy)11.3Nb0.7 compounds with R=Y, Tb, and Dy have been investigated in the concentration region defined by 0.6&amp;lt;x&amp;lt;0.8 and y⩽0.3, where the compounds are single phase with the ThMn12-type of structure. The Curie temperature TC of the RFe12−xNbx compounds is almost independent of the Nb content whereas the saturation magnetization Ms decreases with increasing Nb content. The spin-reorientation temperature Tsr of the TbFe12−xNbx and DyFe12−xNbx compounds decreases monotonically with increasing x. Substitution of Co for Fe in RFe11.3Nb0.7 leads to a remarkable increase of TC and the appearance of a maximum in the Co-concentration dependence of Ms. In contrast, Tsr decreases monotonically with increasing Co content for both R=Tb and Dy. The modification of T- and R-sublattice anisotropy originating from a change of the Nb content and from substitution of Co for Fe was analyzed by combining crystalline electric field theory and the individual-site model.