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The Mn1.2Fe0.8P0.6Si0.4B0.05 alloys were prepared by ball milling and melt-spinning methods. The structure and magnetic characteristics of all samples were examined by X-ray diffraction, vibrating sample magnetometer and SEM. Results show that both the ribbon and bulk alloys can crystallize in a hexagonal Fe2P-type phase with some impurity phase. The lattice parameters, a and c, of Fe2P-type phase are 6.02960 A, 6.03033 A, and 3.42310 A, 3.44431 A for ribbon and bulk Mn1.2Fe0.8P0.6Si0.4B0.05 alloys, respectively. The Curie temperature increased by 20% from 165 K in bulk to 197 K in ribbon while thermal hysteresis and magnetic hysteresis decreased by 28% and 80% for ribbon sample, respectively. Moreover, the values of magnetic entropy change can be tuned from 15.7 J⋅kg−1⋅K−1 in bulk to 21.8 J⋅kg−1⋅K−1 in ribbon under 0–5 T, resulting in the effective refrigerant capacity (RCE) increasing from 238 to 286 J⋅kg−1. The nature of the phase transitions was studied through the Arrott plots, indicating that the samples undergo first-order ferro-paramagnetic phase transitions. The origin of magnetic hysteresis losses is also discussed deeply. Furthermore, this alloys with large magnetic entropy change could be an interest potential for future magnetic refrigeration applications.

The crystal structure of new Lu14Co3In3-type {Gd, Tb, Lu}14Ni3Al3 compounds (P42/nmc. N 137, tP80) has been established using powder X-ray diffraction studies with cell parameters a = 0.95765(2) nm, c = 2.30214(5) nm for Gd14Ni3Al3, a = 0.95012(5) nm, c = 2.28190(10) nm for Tb14Ni3Al3 and a = 0.92604(2) nm, c = 2.23350(4) nm for Lu14Ni3Al3. Magnetic properties of the polycrystalline Y14Co3Al3, Gd14Co3.2Al2.8 and {Tb, Dy}14{Co, Ni}3Al3 have been studied by magnetization measurements. Y14Co3Al3 is paramagnetic down to 2 K, Gd14Co3.2Al2.8 exhibits ferro-antiferromagnetic ordering, while {Tb, Dy}14{Co, Ni}3Al3 show field sensitive pure antiferromagnetic ordering with field induced slight ferromagnetism. Heat capacity measurements (in zero applied magnetic field and field of 50 kOe) confirm metamagnetic-like transitions of Tb14Ni3Al3 and Dy14Ni3Al3.

The aim of this study was to investigate the effect of nickel and cobalt cations on magnetic properties of manganese-zinc ferrite (MZF) nanoparticles. The nanoparticles were produced through sol-gel combustion process with citric acid as the fuel. Then the obtained nanoparticles were calcinated for 30 min at 500 °C. In order to characterize the compounds, four methods were employed, including X-ray diffraction (XRD), vibrating sample magnetometer (VSM), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Spinel formation was confirmed by XRD and it was shown that the crystallite size in all samples was less than 12 nm (nm). In addition, FESEM images revealed that the nanoparticle size was less than 70 nm after calcination. Saturation magnetization (MS) and coercivity (HC) of the MZF nanoparticles are increased by adding Ni and Co cations.

Several new MgZn2-type Laves phases with the P63/mmc symmetry and RE(Co0.667Ga0.333)2 stoichiometries (RE = Gd, Tb, Dy, Ho, and Er) were obtained by arc-melting and subsequent annealing. Single crystals with the MgZn2-type structure were extracted from the annealed RE(Co0.667Ga0.333)2 (RE = Gd, Tb, Dy, and Ho) alloys and Ga flux-grown Er(Co0.667Ga0.333)2 sample. Powder and single-crystal X-ray diffraction methods were used for the phase analysis and structural characterization. A decrease in the cell volume due to the lanthanide contraction is observed from Gd(Co0.667Ga0.333)2 to Er(Co0.667Ga0.333)2. RE atoms occupy the 4f site, while Co and Ga are in the 2a and 6h sites. Magnetic behavior of the hexagonal MgZn2-type RE(Co0.667Ga0.333)2 phases strongly depends on the RE. Apparent ferromagnetic transition is observed for RE = Gd, Tb, and Dy, while the other two phases (RE = Ho, and Er) seem to be ferrimagnetic. Magnetocaloric properties of the Gd(Co0.667Ga0.333)2 phase were measured; the small isothermal magnetic entropy change (ΔSiso) value of −4.94 J/kgK at 152 K and for a ΔH = 0–50 kOe field change suggests a conventional magnetocaloric effect.

Magnetic measurements and neutron powder diffraction investigations on the Y 3 NiSi 3 -type R 3 NiSi 3 compounds ( R =Gd, Tb, Dy) reveal their complex antiferromagnetic ordering. Magnetic measurements on Gd 3 NiSi 3 , Tb 3 NiSi 3 and Dy 3 NiSi 3 indicate antiferromagnetic-like transition at temperatures 260 K, 202 K and 140 K, respectively. Also, the Tb 3 NiSi 3 and Dy 3 NiSi 3 compounds show spin-reorientation transition at 132 K and 99 K, respectively. Below the spin-reorientation transition, the isothermal magnetization curves indicate the metamagnetic-like behavior of Tb 3 NiSi 3 and Dy 3 NiSi 3 . The magnetocaloric effect of Dy 3 NiSi 3 is calculated in terms of isothermal magnetic entropy change and it reaches a maximum value of −1.2 J/kg K and −1.1 J/kg K for a field change of 50 kOe near 146 K and 92 K, respectively. The neutron diffraction studies of Tb 3 NiSi 3 suggest the magnetic ordering of the Tb2 4 j sublattice and no magnetic ordering of the Tb1 2 a sublattice. Tb 3 NiSi 3 transforms from the high temperature paramagnetic state to the commensurate high-temperature a - and c -axis antiferromagnet of I′2/m magnetic space group below 250 K. Below 150 K, the high-temperature antiferromagnet transforms into the low-temperature a -, b - and c -axis antiferromagnet of I′i magnetic space group. At 1.5 K, the terbium magnetic moment in Tb2 sublattice and its a -, b - and c -axis components reach the values of M Tb2 =8.2(1) μ B , M a Tb2 =5.9(1) μ B , M b Tb2 =4.3(2) μ B and M c Tb2 =3.7(2) μ B , respectively.

The structure, magnetic properties, and magnetocaloric effect (MCE) of polycrystalline Ho3M (M = Rh, Ru) compounds have been investigated by X-ray diffraction and magnetization measurements. The Ho3Rh sample contains two phases Ho3Rh and Ho7Rh3. Two successive magnetic transitions near 34 and 22 K from the Ho3Rh and Ho7Rh3 phases, respectively, are observed. The maximum magnetic entropy change (-ΔSM) and refrigerant capacity (RC) of the as-cast Ho3Rh alloy are 10.0 J/kg K and 320 J/kg, respectively, for the magnetic field change of 50 kOe. For the Ho3Ru sample, two phases, Ho3Ru, Ho5Ru2, and trace of Ho2O3, are present. Only one Neel transition temperature around 14 K was observed in this multiple-phase sample. The maximal −ΔSM value is 5.1 J/kg K around TN and the value of RC is estimated to be 145 J/kg for ΔH = 50 kOe, which is less than that of the Ho3Rh sample due to the dominant antiferromagnetic interaction. The excellent magnetocaloric performance suggests the potential applicability of Ho3Rh for magnetic refrigeration at low temperatures.

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The novel Tb 3 NiSi 2 phase adopts the La 3 NiGe 2 -type structure ( Pnma , N 62 , oP24 ). According to the thermal dependence of the magnetization measurements in 100 Oe applied field, Tb 3 NiSi 2 undergoes a ferromagnetic-like transition at 135 K and a spin-orientation transition at 53 K. Based on the neutron diffraction studies in a zero applied field, Tb 3 NiSi 2 shows four types of mixed ferromagnetic–antiferromagnetic ordering below ~130 K, 82 K, 66 K and 53 K. The unit cell of Tb 3 NiSi 2 undergoes an isotropic compression down to 143 K and an anisotropic one below the temperature of the ferromagnetic transition at ~130 K: the a cell parameter increases, whereas the b and c cell parameters and unit cell volume decrease with the decreasing temperature. At 1.5 K the terbium magnetic moment reaches the value 9.1(1) μ B .

The Gd 5 Ge 4− x P x ( x =0.25–0.63) phases were synthesized and found to adopt the Sm 5 Ge 4 -type structure with broken interslab (Ge,P)–(Ge,P) dimers. According to the single crystal X-ray diffraction, substitution of the P for Ge atoms occurs only on the interslab site. Electronic band structure calculations performed with the tight-binding, linear-muffin-tin-orbital method using the atomic sphere approximation confirmed the experimental site preference for the P atoms. Magnetization measurements indicated that all the Gd 5 Ge 4− x P x samples are ferromagnetic with Curie temperatures ranging from 64 to 101 K. The ferromagnetic coupling in the samples increases with the P amount, and this is related to an increase in the valence electron concentration. A Griffiths-type phase is observed in the paramagnetic regions for all samples and its stability is discussed.

We present a neutron powder diffraction investigation of the magnetic structure of La 3 NiGe 2 -type Tb 3 NiGe 2 and Mn 5 Si 3 -type Tb 5 Ni x Ge 3− x ( x =0, 0.3) compounds. It is found that below∼135 K Tb 3 NiGe 2 exhibits a commensurate b -collinear ferrimagnetic ordering with C 2h ′={ 1 , m z , 1′× 2 z , 1′× 1 } magnetic point group. The Mn 5 Si 3 -type Tb 5 Ge 3 and Tb 5 Ni 0.3 Ge 2.7 compounds are found to present a flat spiral type antiferromagnetic ordering at 85 and ≥89 K, respectively. The Ni for Ge substitution is found to decrease the flat spiral ordered magnetic unit cell from a × a ×40 c of Tb 5 Ge 3 (below 40 K) down to a × a ×5 c for Tb 5 Ni 0.3 Ge 2.7 (below ∼10 K).

Small single crystals of the Fe 1.14(7) Cr 1.86(8) Se 4.0(2) ferrimagnet were grown using chemical vapor transport. Fe 1.14 Cr 1.86 Se 4 adopts the Cr 3 S 4 structure with two metal sites. The magnetic behavior of Fe 1.14 Cr 1.86 Se 4 can be described by two magnetic sublattices with different magnetization values and different temperature dependencies. Depending on the experimental conditions, such as the strength and direction of the cooling field, magnetization reversal, large negative magnetization and high-temperature compensation point may result. If the cooling field exceeds 1.5 Oe, magnetization reversal occurs at low temperatures. If the cooling and applied fields are opposite, a large negative magnetization and high-temperature compensation point are observed.

Substitution of Sb for Si in the Gd 5 Si 4 phase results in the formation of ternary Gd 5 Si 4− x Sb x phases with three different structure types. For x ≤0.38 the Gd 5 Si 4 -type structure ( Pnma space group) with all interslab T-T dimers intact exists ( T is Si or Si/Sb mixture), in the x =1.21–1.79 region the Sm 5 Ge 4 -type structure ( Pnma ) with all interslab dimers broken is found. A further increase in the Sb concentration ( x =2.27–3.1) leads to the appearance of the Eu 5 As 4 -type structure ( Cmca ) with broken but equivalent interslab T⋯T bonds. The Gd 5 Si 4− x Sb x phases with 1.21≤ x ≤3.1 undergo ferromagnetic transitions in the temperature range from 164 to 295 K. Magnetocaloric effect in terms of the isothermal entropy change, Δ S , reaches the maximum values of -3.7(4), -4.2(6) and -4.6(7) J/kg K for the Gd 5 Si 2 Sb 2 , Gd 5 Si 1.5 Sb 2.5 and Gd 5 SiSb 3 samples, respectively.