Magnetism of R2Ti3Ge4 (R=Sc, Gd, Tb, Dy, Ho, and Er) compounds
25 May 2004-Journal of Applied Physics (American Institute of Physics)-Vol. 95, Iss: 11, pp 7079-7081
TL;DR: In this paper, the results of magnetization measurements down to 1.8 K on polycrystalline R2Ti3Ge4 (R=Sc, Gd, Tb, Dy, Ho, and Er) compounds of orthorhombic Sm5Ge4-type (space group Pnma) are presented and discussed.
Abstract: Results of magnetization measurements down to 1.8 K on polycrystalline R2Ti3Ge4 (R=Sc, Gd, Tb, Dy, Ho, and Er) compounds of orthorhombic Sm5Ge4-type (space group Pnma) are presented and discussed. Gd2Ti3Ge4 is found to be a ferromagnet below 32 K while other R2Ti3Ge4 compounds, with magnetic rare earths (R=Tb, Dy, Ho, and Er), undergo a low temperature antiferromagnetic transition. The effective magnetic moment (μeff) values obtained from the Curie–Weiss paramagnetic susceptibility correspond to that of R3+ ions. Saturation of magnetization is not observed upto applied fields of 5.5 T at 1.8 K for all R2Ti3Ge4 compounds except Gd2Ti3Ge4, indicating the possible presence of crystal field effects. Electrical resistivity of these compounds is dominated by electron-phonon scattering above 20 K and signature of phonon and magnon drag effects are seen in the low temperature thermopower data.
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TL;DR: In this article, the heat capacity of polycrystalline R2Ti3Ge4 (R=Gd, Tb, and Er) compounds has been studied in the temperature range of 18-300K in various applied magnetic fields.
Abstract: The heat capacity of polycrystalline R2Ti3Ge4 (R=Gd, Tb, and Er) compounds (orthorhombic, Sm5Ge4-type, space group Pnma) has been studied in the temperature range of 18–300K in various applied magnetic fields The compounds with magnetic lanthanide elements show interesting low field magnetism intrigued by the possible presence of competing antiferromagnetic and ferromagnetic interactions The magnetocaloric effect in these compounds is estimated from the field dependent heat capacity data The magnetic entropy change and the adiabatic temperature change in the vicinity of the magnetic transition are found to be significant
3 citations
TL;DR: In this article, the electronic and magnetic properties of the RE 2 Ti 3 Si 4 (RE=Gd, Tb, Er) compounds have been investigated by means of LSDA+U method which is based on the density functional theory (DFT).
Abstract: Electronic and magnetic properties of the RE 2 Ti 3 Si 4 (RE = Gd, Tb, Er) compounds have been investigated by means of LSDA + U method which is based on the density functional theory (DFT). Excellent agreement is obtained between the calculated and experimental values for the structural parameters, which indicates that the method we used at the present is reasonable. Mulliken analysis shows that RE (RE = Gd, Er) and Ti atoms lose charges while Si obtain charges. From the analysis of the density of states for the RE 2 Ti 3 Si 4 (RE = Gd, Tb, Er) compounds, we can make the conclusion that Si mainly contributes to the bonding states, while Ti and RE contribute to the anti-bonding states. RE atoms exhibit strong magnetism, Ti atoms exhibit different magnetic strength in different compounds, while Si is non-magnetic because all the subshells are completely occupied by the majority and minority spin. In order to obtain believable magnetic moments, we revised our calculated results and realized expected values.
3 citations
TL;DR: In this article, the magnetocaloric effect of polycrystalline R2Ti3Ge4 (R = Gd, Tb and Er) compounds (Orthorhombic, Sm5Ge4-type, Space group Pnma) was studied in the temperature range of 1.8 K to 300 K in various applied magnetic fields.
Abstract: Heat capacity of polycrystalline R2Ti3Ge4 (R = Gd, Tb and Er) compounds (Orthorhombic, Sm5Ge4-type, Space group Pnma) has been studied in the temperature range of 1.8 K to 300 K in various applied magnetic fields. The compounds with magnetic lanthanide elements show interesting low field magnetism intrigued by possible presence of competing antiferromagnetic and ferromagnetic interactions. The magnetocaloric effect in these compounds is estimated from the field dependent heat capacity data. The magnetic entropy change and the adiabatic temperature change in the vicinity of the magnetic transition are found to be significant.
2 citations
TL;DR: X-ray diffraction on single crystal performed on Gd 2 Sc 3 Si 4 reveals that this ternary silicide crystallizes as Gd2 Sc 3 Ge 4 in the orthorhombic Ce 2 Sc3 Si 4 -type with a small deficiency in gadolinium leading to the formula Gd 1.88(1) Sc 3 si 4 as mentioned in this paper.
Abstract: X-ray diffraction on single crystal performed on Gd 2 Sc 3 Si 4 reveals that this ternary silicide crystallizes as Gd 2 Sc 3 Ge 4 in the orthorhombic Ce 2 Sc 3 Si 4 -type with a small deficiency in gadolinium leading to the formula Gd 1.88(1) Sc 3 Si 4 . The structure is formed by [Gd 2 Sc 3 Si 4 ] slabs with Si–Si interslab covalent bonds. The investigation of the Gd 2 Sc 3 Si 4 and Gd 2 Sc 3 Ge 4 compounds by magnetization, electrical resistivity and specific heat measurements reveals their antiferromagnetic behaviors; Gd 2 Sc 3 Si 5 having a Neel temperature (48–52 K) higher than that observed (22–23 K) for Gd 2 Sc 3 Ge 4 .
2 citations
TL;DR: In this article, the effect of Mo substitution at the Ti site of orthorhombic Sm5Ge4-type R2Ti3Ge4 compounds on the magnetic and electrical transport properties has been studied.
Abstract: The effect of Mo substitution at Ti site of orthorhombic Sm5Ge4-type R2Ti3Ge4 compounds on the magnetic and electrical transport properties has been studied. The Tb2Ti3−xMoxGe4 (x=0.3,0.75) and Er2Ti2.7Mo0.3Ge4 compounds have been synthesized and it is found that these compounds retain parent crystal structure at room temperature (space group Pnma, No. 62). Mo substitution decreases the antiferromagnetic ordering temperature (TN) of Tb2Ti3Ge4 compound from ∼18 to ∼13 and ∼10 K, respectively, for x=0.3 and 0.75. The Er2Ti2.7Mo0.3Ge4 compound shows a tendency to order at ∼2 K, whereas the parent Er2Ti3Ge4 is magnetically ordered at 3 K. Magnetization versus field data of Tb2Ti3−xMoxGe4 (x=0.3,0.75) reveal soft ferromagnetic nature. The metamagnetic transition that is present in parent Tb2Ti3Ge4 is found to disappear with Mo substitution. Magnetization value reaches ∼6.2μB/Tb3+ at 2 K in fields of 8 T, indicating incomplete ferromagnetic ordering with or without an antiferromagnetic component. Electrical res...
1 citations
References
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TL;DR: An extremely large magnetic entropy change has been discovered in magnetic materials when subjected to a change in the magnetic field as mentioned in this paper, which exceeds the reversible magnetocaloric effect in any known magnetic material by at least a factor of 2.
Abstract: An extremely large magnetic entropy change has been discovered in $\mathrm{Gd}{}_{5}(\mathrm{Si}{}_{2}\mathrm{Ge}{}_{2})$ when subjected to a change in the magnetic field. It exceeds the reversible (with respect to an alternating magnetic field) magnetocaloric effect in any known magnetic material by at least a factor of 2, and it is due to a first order $[\mathrm{ferromagnetic}(\mathrm{I})\ensuremath{\leftrightarrow}\mathrm{ferromagnetic}(\mathrm{II})]$ phase transition at 276 K and its unique magnetic field dependence.
3,561 citations
TL;DR: In this article, the effect of different alloying additions substituting for nonmagnetic Si and Ge on the giant magnetocaloric effect observed for the compound Gd5(Si2Ge2) was studied.
Abstract: A study of the effect of different alloying additions substituting for nonmagnetic Si and Ge on the giant magnetocaloric effect observed for the compound Gd5(Si2Ge2) revealed that small amounts (∼ 0.33 at%) of Ga raise the Curie temperature and preserve the giant magnetocaloric effect. Larger quantities of Ga lead to a significant reduction in the magnetocaloric effect, but the Curie temperature continues to rise. Many 3d-metal and p-element additions also reduce the magnetocaloric effect in Gd5(Si2Ge2) due to the changes in the thermodynamic nature of the magnetic phase transition. In general, all alloying additions raise the Curie temperature of the parent Gd5(Si2Ge2).
301 citations
TL;DR: In this article, powder X-ray diffraction and susceptibility measurements on ternary germanides RTiGe (R≡La-Nd, Sm, Lu) are reported.
Abstract: Investigations made by powder X-ray diffraction and susceptibility measurements on ternary germanides RTiGe (R≡La–Nd, Sm, Lu) are reported. All these new compounds crystallize in the well-known tetragonal structure of the CeFeSi-type (space group P4/nmm). LaTiGe and LuTiGe are Pauli paramagnets. CeTiGe is characterized by Curie–Weiss paramagnetism down to 5 K, whereas PrTiGe, NdTiGe and SmTiGe behave antiferromagnetically below 70, 150 and 265 K, respectively. Low temperature (T<77 K) investigations of the corresponding heavy rare earth compounds show that ErTiGe and TmTiGe are antiferromagnetic below 41 and 15 K, respectively. Metamagnetic-like behaviour occurs in ErTiGe, TmTiGe (Hc≅2 kOe) and HoTiGe (Hc≅5 kOe). These results are discussed and compared with those of isotypic ternary RTX (T≡Mn, Fe, Co, Ru; X≡Si, Ge) compounds.
32 citations
TL;DR: In this article, powder X-ray diffraction investigations and macroscopic magnetic properties of new ternary Sc 2 Re 3 Si 4 -type R 2 Ti 3 Si4 compounds (R=Gd-Er) are reported.
Abstract: Powder X-ray diffraction investigations and macroscopic magnetic properties of new ternary Sc 2 Re 3 Si 4 -type R 2 Ti 3 Si 4 compounds (R=Gd–Er) are reported. The compounds (Gd 0.95 ) 2 Ti 3 Si 4 ( a =0.6997(2) nm, c =1.2878(4) nm), Tb 2 Ti 3 Si 4 ( a =0.7006(1) nm, c =1.2875(2) nm), Dy 2 Ti 3 Si 4 ( a =0.6976(1) nm, c =1.2814(2) nm), Ho 2 Ti 3 Si 4 ( a =0.6970(1) nm, c =1.2793(2) nm) and Er 2 Ti 3 Si 4 ( a =0.6964(1) nm, c =1.2777(1) nm) crystallize in the tetragonal Sc 2 Re 3 Si 4 -type structure (space group P 4 1 2 1 2; No. 96). The Gd 2 Ti 3 Si 4 , Tb 2 Ti 3 Si 4 and Er 2 Ti 3 Si 4 compounds are Curie–Weiss paramagnets down to 4 K.
21 citations
TL;DR: In this paper, the magnetic moments of polycrystalline RTiGe (R=Pr, Nd, Tb, Dy, HoTiGe, ErTiGe and Tb−Er) samples were analyzed.
Abstract: Neutron diffraction experiments were carried out on polycrystalline RTiGe (R=Pr, Nd, Tb–Er) samples. These compounds crystallise with the tetragonal CeFeSi-type structure (space group P4/nmm). This structure is closely related to the ThCr 2 Si 2 -type and can be described as “BaAl 4 blocks” connected via R–R contacts (“W blocks”). All the compounds are antiferromagnetic. PrTiGe and NdTiGe are characterised by an easy-plane sine-modulated structure characterised by a wave vector k =0,0, q z =0.242 and 0.334 below 62 and 128 K, respectively. Below 80 K, NdTiGe exhibits a commensurate arrangement, which consists on ferromagnetic (0 0 1) Nd layers coupled antiferromagnetically along the c direction with the sequence ++−−. This commensurate magnetic ordering also occurs in TbTiGe, DyTiGe, HoTiGe and ErTiGe below 312, 185, 124 and 36 K, respectively. In the first three compounds (R=Tb−Ho), the magnetic moment is aligned along the c -axis whereas it is localised in the basal plane in ErTiGe. In all the RTiGe compounds, the magnitude of the ordered moments at 2 K amounts nearly to the free ion magnetic moment ( gJ ) values for the respective R 3+ ions.
20 citations