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Title: Electronically- and crystal-structure-driven magnetic structures and physical properties of RScSb (R = rare earth) compounds. A neutron diffraction, magnetization and heat capacity study

Abstract

The synthesis of the new equiatomic RScSb ( R = La-Nd, Sm, Gd-Tm, Lu, Y) compounds has been recently reported. These rare earth compounds crystallize in two different crystal structures, adopting the CeScSi-type ( I 4/ mmm) for the lighter R (La-Nd, Sm) and the CeFeSi-type (P4 /nmm) structure for the heavier R ( R = Gd-Tm, Lu, Y). Here we report the results of neutron diffraction, magnetization and heat capacity measurements on some of these compounds ( R = Ce, Pr, Nd, Gd and Tb). Band structure calculations have also been performed on CeScSb and GdScGe (CeScSi-type), and on GdScSb and TbScSb (CeFeSi-type) to compare and understand the exchange interactions in CeScSi and CeFeSi structure types. The neutron diffraction investigation shows that all five compounds order magnetically, with the highest transition temperature of 66 K in TbScSb and the lowest of about 9 K in CeScSb. The magnetic ground state is simple ferromagnetic (τ = [0 0 0]) in CeScSb, as well in NdScSb for 32 >T > 22 K. Below 22 K a second magnetic transition, with propagation vector τ = [¼ ¼ 0], appears in NdScSb. PrScSb has a magnetic structure within, determined by mostly ferromagnetic interactionsmore » and antiferromagnetic alignment of the Pr-sites connected through the I-centering ( τ = [1 0 0]). A cycloidal spiral structure with a temperature dependent propagation vector τ = [δ δ ½] is found in TbScSb. The results of magnetization and heat capacity lend support to the main conclusions derived from neutron diffraction. As inferred from a sharp peak in magnetization, GdScSb orders antiferromagnetically at 56 K. First principles calculations show lateral shift of spin split bands towards lower energy from the Fermi level as the CeScSi-type structure changes to the CeFeSi-type structure. This rigid shift may force the system to transform from exchange split ferromagnetic state to the antiferromagnetic state in RScSb compounds (as seen for example in GdScSb and TbScSb) and is proposed to explain the change-over from a ferromagnetic structure as found in the CeScSi-type compounds CeScSb and NdScSb to the antiferromagnetic state as found in TbScSb and GdScSb.« less

Authors:
 [1];  [2];  [2];  [3];  [4];  [3];  [5]
  1. Institut Lauer-Langevin, Grenoble (France)
  2. TIFR, Mumbai (India)
  3. Inst. SPIN-CNR, Genova (Italy); Univ. of Genova (Italy); Ames Lab., Ames, IA (United States)
  4. Ames Lab., Ames, IA (United States)
  5. Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1166718
Report Number(s):
IS-J 8456
Journal ID: ISSN 0953-8984
DOE Contract Number:
AC02-07CH11358
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physics. Condensed Matter; Journal Volume: 26; Journal Issue: 36
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Ritter, C, Dhar, S K, Kulkarni, R, Provino, A, Paudyal, Durga, Manfrinetti, Pietro, and Gschneidner, Karl A. Electronically- and crystal-structure-driven magnetic structures and physical properties of RScSb (R = rare earth) compounds. A neutron diffraction, magnetization and heat capacity study. United States: N. p., 2014. Web. doi:10.1088/0953-8984/26/36/366001.
Ritter, C, Dhar, S K, Kulkarni, R, Provino, A, Paudyal, Durga, Manfrinetti, Pietro, & Gschneidner, Karl A. Electronically- and crystal-structure-driven magnetic structures and physical properties of RScSb (R = rare earth) compounds. A neutron diffraction, magnetization and heat capacity study. United States. doi:10.1088/0953-8984/26/36/366001.
Ritter, C, Dhar, S K, Kulkarni, R, Provino, A, Paudyal, Durga, Manfrinetti, Pietro, and Gschneidner, Karl A. Thu . "Electronically- and crystal-structure-driven magnetic structures and physical properties of RScSb (R = rare earth) compounds. A neutron diffraction, magnetization and heat capacity study". United States. doi:10.1088/0953-8984/26/36/366001.
@article{osti_1166718,
title = {Electronically- and crystal-structure-driven magnetic structures and physical properties of RScSb (R = rare earth) compounds. A neutron diffraction, magnetization and heat capacity study},
author = {Ritter, C and Dhar, S K and Kulkarni, R and Provino, A and Paudyal, Durga and Manfrinetti, Pietro and Gschneidner, Karl A},
abstractNote = {The synthesis of the new equiatomic RScSb ( R = La-Nd, Sm, Gd-Tm, Lu, Y) compounds has been recently reported. These rare earth compounds crystallize in two different crystal structures, adopting the CeScSi-type ( I 4/ mmm) for the lighter R (La-Nd, Sm) and the CeFeSi-type (P4 /nmm) structure for the heavier R ( R = Gd-Tm, Lu, Y). Here we report the results of neutron diffraction, magnetization and heat capacity measurements on some of these compounds ( R = Ce, Pr, Nd, Gd and Tb). Band structure calculations have also been performed on CeScSb and GdScGe (CeScSi-type), and on GdScSb and TbScSb (CeFeSi-type) to compare and understand the exchange interactions in CeScSi and CeFeSi structure types. The neutron diffraction investigation shows that all five compounds order magnetically, with the highest transition temperature of 66 K in TbScSb and the lowest of about 9 K in CeScSb. The magnetic ground state is simple ferromagnetic (τ = [0 0 0]) in CeScSb, as well in NdScSb for 32 >T > 22 K. Below 22 K a second magnetic transition, with propagation vector τ = [¼ ¼ 0], appears in NdScSb. PrScSb has a magnetic structure within, determined by mostly ferromagnetic interactions and antiferromagnetic alignment of the Pr-sites connected through the I-centering ( τ = [1 0 0]). A cycloidal spiral structure with a temperature dependent propagation vector τ = [δ δ ½] is found in TbScSb. The results of magnetization and heat capacity lend support to the main conclusions derived from neutron diffraction. As inferred from a sharp peak in magnetization, GdScSb orders antiferromagnetically at 56 K. First principles calculations show lateral shift of spin split bands towards lower energy from the Fermi level as the CeScSi-type structure changes to the CeFeSi-type structure. This rigid shift may force the system to transform from exchange split ferromagnetic state to the antiferromagnetic state in RScSb compounds (as seen for example in GdScSb and TbScSb) and is proposed to explain the change-over from a ferromagnetic structure as found in the CeScSi-type compounds CeScSb and NdScSb to the antiferromagnetic state as found in TbScSb and GdScSb.},
doi = {10.1088/0953-8984/26/36/366001},
journal = {Journal of Physics. Condensed Matter},
number = 36,
volume = 26,
place = {United States},
year = {Thu Aug 14 00:00:00 EDT 2014},
month = {Thu Aug 14 00:00:00 EDT 2014}
}
  • We report the results of an extensive investigation of the magnetic properties of a large series of undoped {ital R}{sub 2}CuO{sub 4} single crystals with {ital R}==Pr, Nd, Sm, Eu, and Gd (which are the host compounds for the newly discovered series of electron cuprate superconductors) and mixture versions of the form {ital A}{sub 2{minus}{ital x}}B{sub x}CuO{sub 4}, with {ital A}==Pr, Nd, Sm, Eu, or Gd, and {ital B}==Gd, Tb, or Dy. We have measured dc and ac magnetization, microwave magnetoabsorption, EPR, and specific heat. These measurements reveal two characteristic transition temperatures associated with a novel complex magnetic behavior, includingmore » weak ferromagnetism, two sharp peaks in the low-field dc magnetization, an unusual anisotropy in the EPR resonance field for {ital R}=Gd, and two additional anisotropic microwave absorption modes. The higher characteristic transition temeperature at {similar to}270 K is associated with antiferromagnetic ordering of the Cu moments which are strongly coupled within the CuO{sub 2} layers. The lower, at {le}20 K, cannot be attributed to antiferromagnetic ordering of the {ital R} moments and is tentatively attributed to a spontaneous canted spin reorientation. An understanding of this magnetic behavior is important in order to ascertain its relationship to possible mechanisms of high-temperature superconductivity.« less
  • The ternary rare-earth boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Y, Gd-Lu) were prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for 1 month. The crystal structures of Tb{sub 15}B{sub 4}C{sub 14} and Er{sub 15}B{sub 4}C{sub 14} were determined from single crystal X-ray diffraction data. They crystallize in a new structure type in space group P4/mnc (Tb{sub 15}B{sub 4}C{sub 14}: a=8.1251(5) A, c=15.861(1) A, Z=2, R{sub 1}=0.041 (wR{sub 2}=0.088) for 1023 reflections with I{sub o}>2{sigma}(I{sub o}); Er{sub 15}B{sub 4}C{sub 14}: a=7.932(1) A, c=15.685(2) A, Z=2, R{sub 1}=0.037 (wR{sub 2}=0.094) for 1022 reflections with I{submore » o}>2{sigma}(I{sub o})). The crystal structure contains discrete carbon atoms and bent CBC units in octahedra and distorted bicapped square antiprisms, respectively. In both structures the same type of disorder exists. One R atom position needs to be refined as split atom position with a ratio 9:1 indicative of a 10% substitution of the neighboring C{sup 4-} by C{sub 2}{sup 4-}. The actual composition has then to be described as R{sub 15}B{sub 4}C{sub 14.2}. The isoelectronic substitution does not change the electron partition of R{sub 15}B{sub 4}C{sub 14} which can be written as (R{sup 3+}){sub 15}(C{sup 4-}){sub 6}(CBC{sup 5-}){sub 4{center_dot}}e{sup -}. The electronic structure was studied with the extended Hueckel method. The investigated compounds Tb{sub 15}B{sub 4}C{sub 14}, Dy{sub 15}B{sub 4}C{sub 14} and Er{sub 15}B{sub 4}C{sub 14} are hard ferromagnets with Curie temperatures T{sub C}=145, 120 and 50 K, respectively. The coercive field B{sub C}=3.15 T for Dy{sub 15}B{sub 4}C{sub 14} is quite remarkable. - Graphical abstract: The ternary rare earth boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Y, Gd-Lu) were prepared from the elements by arc-melting followed by annealing in silica tubes at 1270 K for 1 month. Tb{sub 15}B{sub 4}C{sub 14} is a new member of the rare-earth metal boride carbide series in which the finite quasi-molecular CBC entities as well as isolated C atoms are embedded in the voids of the metal atom matrix. The structure of Tb{sub 15}B{sub 4}C{sub 14} contains two types of slabs: one slab contains finite bent CBC units and isolated carbon atoms whereas another is formed only from octahedral coordinated single carbon atoms. The electronic structure for the idealized composition corresponds to an electron partitioning according to (Tb{sup 3+}){sub 15}(C{sup 4-}){sub 6}(CBC{sup 5-}){sub 4{center_dot}}e{sup -} giving rise to a single electron per formula for Tb-Tb framework bonding. The magnetism of the ternary rare earth boride carbides R{sub 15}B{sub 4}C{sub 14} (R=Tb, Dy, Er) is characterized by the onset of ferromagnetic order below T<150 K.« less
  • Eleven new compounds, R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) and R Pd{sub 2}Cd{sub 20} (R=Ce, Pr, Sm), were grown as single crystals in high temperature cadmium-rich solutions. They crystallize in the cubic CeCr{sub 2}Al{sub 20}-type structure (Fd3{sup ¯}m, Z=8) as characterized by measurements of powder X-ray diffraction. Electrical resistivity, magnetization, and specific heat measurements were performed on R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) single crystals. Whereas YNi{sub 2}Cd{sub 20} and LaNi{sub 2}Cd{sub 20} exhibit unremarkable metallic behavior, when magnetic moments from localized 4f electron states (Gd{sup 3+}–Tb{sup 3+}) are embedded into this host, theymore » exhibit ferromagnetic order with values of the Curie temperature T{sub C} for R Ni{sub 2}Cd{sub 20} (R=Gd, and Tb) which scale with the de Gennes factor. - Graphical abstract: Specific heat divided by temperature C/T vs. T for single crystals of R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Gd, and Tb). Left inset: Low temperature C/T vs. T{sup 2} for LaNi{sub 2}Cd{sub 20}. The solid line represents a linear fit of the data. Right inset: Low-temperature C/T data vs. T for R=Ce–Nd, Gd, and Tb; magnetic ordering temperatures are indicated by arrows. - Highlights: • R Ni{sub 2}Cd{sub 20} (R=Y, La–Nd, Sm, Gd, Tb) single crystals synthesized for the first time. • R Pd{sub 2}Cd{sub 20} (R=Ce, Pr, Sm) single crystals synthesized for the first time. • Single crystals are of good metallurgical quality (large RRR values). • NdNi{sub 2}Cd{sub 20} orders antiferromagnetically at T{sub N}=1.5 K. • R Ni{sub 2}Cd{sub 20} (R=Sm, Gd, Tb) order ferromagnetically.« less
  • A series of binary rare-earth metal silicides RE {sub 5}Si{sub 3} and ternary boron-interstitial phases RE {sub 5}Si{sub 3}B {sub x} (RE=Gd, Dy, Ho, Lu, and Y) adopting the Mn{sub 5}Si{sub 3}-type structure, have been prepared from the elemental components by arc melting. Boron 'stuffed' phases were subsequently heated at 1750 K within a high-frequency furnace. Crystal structures were determined for both binary and ternary series of compounds from single-crystal X-ray data: hexagonal symmetry, space group P6{sub 3}/mcm, Z=2. Boron insertion in the host binary silicides results in a very small decrease of the unit cell parameters with respect tomore » those of the binaries. According to X-ray data, partial or nearly full boron occupancy of the interstitial octahedral sites in the range 0.6-1 is found. The magnetic properties of these compounds were characterized by the onset of magnetic ordering below 100 K. Boron insertion induces a modification of the transition temperature and {theta} {sub p} values in most of the antiferromagnetic binary silicides, with the exception of the ternary phase Er{sub 5}Si{sub 3}B {sub x} which was found to undergo a ferromagnetic transition at 14 K. The electrical resistivities for all binary silicides and ternary boron-interstitial phases resemble the temperature dependence of metals, with characteristic changes of slope in the resistivity curves due to the reduced electron scattering in the magnetically ordered states. Zintl-Klemm concept would predict a limiting composition RE {sub 5}Si{sub 3}B{sub 0.6} for a valence compound and should then preclude the stoichiometric formula RE{sub 5}Si{sub 3}B. Density functional theory calculations carried out on some RE {sub 5}Si{sub 3}Z {sub x} systems for different interstitial heteroatoms Z and different x contents from 0 to 1 give some support to this statement. - Graphical abstract: Incorporation of boron in vacant octahedral sites of the Mn{sub 5}Si{sub 3}-type phase Gd{sub 5}Si{sub 3} modifies its resistivity properties.« less