Ferromagnetism and re-entrant spin-glass transition in quasicrystal approximants Au–SM–Gd (SM = Si, Ge)

Hiroto, Takanobu; Gebresenbut, Girma Hailu; Gómez, Cesar Pay; Muro, Yuji; Isobe, Masahiko; Ueda, Yutaka; Tokiwa, Kazuyasu; Tamura, Ryuji

doi:10.1088/0953-8984/25/42/426004

Cited by 55 publications

(42 citation statements)

References 18 publications

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“…Until recently, this lack of long-range magnetic ordering also extended to quasicrystal approximants [7][8][9], which can be viewed as quasicrystalline clusters sitting on a periodic lattice that possesses a translational symmetry. Recently, two exceptions have been identified: ferromagnetic Gd-Au-Si(Ge) [10] and antiferromagnetic RCd 6 [11][12][13][14][15]. The antiferromagnetic RCd 6 compounds in particular have attracted great attention, since they bring up the possibility of related quasicrystal phases that could have long-range magnetic ordering.…”

Section: Introductionmentioning

confidence: 99%

Magnetic and transport properties of i- R -Cd icosahedral quasicrystals (R=Y,Gd-Tm)

et al. 2014

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We present a detailed characterization of the recently discovered i-R-Cd (R=Y,Gd-Tm) binary quasicrystals by means of x-ray diffraction, temperature-dependent dc and ac magnetization, temperature-dependent resistance, and temperature-dependent specific heat measurements. Structurally, the broadening of x-ray diffraction peaks found for i-R-Cd is dominated by frozen-in phason strain, which is essentially independent of R. i-Y-Cd is weakly diamagnetic and manifests a temperature-independent susceptibility. i-Gd-Cd can be characterized as a spin glass below 4.6 K via dc magnetization cusp, a third order nonlinear magnetic susceptibility peak, a frequency-dependent freezing temperature, and a broad maximum in the specific heat. i-R-Cd (R=Ho-Tm) is similar to i-Gd-Cd in terms of features observed in thermodynamic measurements. i-TbCd and i-Dy-Cd do not show a clear cusp in their zero-field-cooled dc magnetization data, but instead show a more rounded, broad local maximum. The resistivity for i-R-Cd is of order 300μΩ cm and weakly temperature dependent. The characteristic freezing temperatures for i-R-Cd (R=Gd-Tm) deviate from the de Gennes scaling, in a manner consistent with crystal electric field splitting induced local moment anisotropy. We present a detailed characterization of the recently discovered i-R-Cd (R = Y, Gd-Tm) binary quasicrystals by means of x-ray diffraction, temperature-dependent dc and ac magnetization, temperature-dependent resistance, and temperature-dependent specific heat measurements. Structurally, the broadening of x-ray diffraction peaks found for i-R-Cd is dominated by frozen-in phason strain, which is essentially independent of R. i-Y-Cd is weakly diamagnetic and manifests a temperature-independent susceptibility. i-Gd-Cd can be characterized as a spin glass below 4.6 K via dc magnetization cusp, a third order nonlinear magnetic susceptibility peak, a frequency-dependent freezing temperature, and a broad maximum in the specific heat. i-R-Cd (R = Ho-Tm) is similar to i-Gd-Cd in terms of features observed in thermodynamic measurements. i-Tb-Cd and i-Dy-Cd do not show a clear cusp in their zero-field-cooled dc magnetization data, but instead show a more rounded, broad local maximum. The resistivity for i-R-Cd is of order 300 μ cm and weakly temperature dependent. The characteristic freezing temperatures for i-R-Cd (R = Gd-Tm) deviate from the de Gennes scaling, in a manner consistent with crystal electric field splitting induced local moment anisotropy. Keywords Physics and Astronomy Disciplines Condensed Matter Physics Magnetic and transport properties of i-R-Cd icosahedral quasicrystals (R=Y, Gd-Tm)

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Section: Introductionmentioning

confidence: 99%

Magnetic and transport properties of i- R -Cd icosahedral quasicrystals (R=Y,Gd-Tm)

et al. 2014

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“…44 Interestingly, the 1/1 cubic approximant of AuSiGd and AuGeGd are both ferromagnetic below a freezing temperature but at even lower temperatures the AuGeGd approximant alone shows an additional transition to a spin-glass. 45 According to current structure models, the major difference is some site disorder of the rare earth atoms in AuGeGd which is not present in the AuSiGd approximant. 46 In general, site disorder of the rare earth atoms is very common in quasicrystals.…”

Section: E Comparison To Experimental Resultsmentioning

confidence: 99%

Long-range magnetic order in models for rare-earth quasicrystals

Thiem

Chalker

2015

Phys. Rev. B

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We take a two-step theoretical approach to study magnetism of rare earth quasicrystals by considering Ising spins on quasiperiodic tilings, coupled via RKKY interactions. First, we compute RKKY interactions from a tight-binding Hamiltonian defined on the two-dimensional quasiperiodic tilings. We find that the magnetic interactions are frustrated and strongly dependent on the local environment. This results in the formation of clusters with strong bonds at certain patterns of the tilings that repeat quasiperiodically. Second, we examine the statistical mechanics of Ising spins with these RKKY interactions, using extensive Monte Carlo simulations. Although models that have frustrated interactions and lack translational invariance might be expected to display spin glass behaviour, we show that the spin system has a phase transition to low-temperature states with long-range quasiperiodic magnetic order. Additionally, we find that in some of the systems spin clusters can fluctuate much below the ordering temperature.PACS numbers: 75.50. Kj, Quasicrystals with their unusual atomic structure characterized by long-range order without a threedimensional translational periodicity 1 are known to have rather exotic physical properties, and so far we lack a good theoretical understanding for many of them. For instance, the electronic properties of this material class include a pseudogap at the Fermi energy 2,3 and multifractal (critical) wave functions 4 resulting in anomalous electronic transport 5,6 . An important question in this context is how these electronic properties influence the magnetism in quasicrystals. 7,8In general, one can distinguish two types of magnetic quasicrystals: those with magnetic moments at (i) transition metal or (ii) rare earth sites. In the first, moment formation is an important aspect of the theoretical problem since they appear only at a small fraction of sites.7 By contrast, the second class suggests a simpler description, with well-defined local moments at concentrations of 5-10% interacting via long-range RKKY interactions which are mediated by the conduction electrons.9,10 Examples of the latter class include the icosahedral i-ZnMgR and i-AgInR materials 9,11 , as well as decagonal d-ZnMgR materials 12 and the recently discovered binary phasesHere we use tight-binding models and Ising models to address this theoretical problem. We examine the form of the RKKY interactions based on a tight-binding Hamiltonian defined on two-dimensional quasiperiodic tilings (see Section I). We find that the coupling between pairs of sites depends not only on their distance but also varies strongly with the local environment on the tiling. Although we find ferromagnetic and antiferromagnetic bonds as in periodic systems, the magnetic interactions do not show a well-defined spatial period with a Fermi wave vector because quasicrystals do not have a Brillouin zone. Second, we study the consequences of these interactions (see Section II), by taking them as exchange constants between Ising spins located at a fr...

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“…It should be noted that intermetallic phases with YCd 6 -type and related structures have been found to exist in many ternary systems. Detailed descriptions of some gold-containing structures are given in [33][34][35][36][37][38].…”

Section: Rau 3±x Ga 3±x Phasesmentioning

confidence: 99%

New ternary phases from the R–Au–Ga systems (R = Gd-Tm)

Verbovytskyy¹,

Cfmc-Ul²

2014

Chem. Met. Alloys

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Twenty rare-earth gold gallides, RAu 3 Ga 7 (ScRh 3 Si 7-type, space group R-3c, Z = 6, hR66), RAu 3±x Ga 3±x (YCd 6-type, space group Im-3, Z = 24, cI68), RAu 1+x Ga 2-x (MgCuAl 2-type, space group Cmcm, Z = 4, oS16) (R = Gd-Tm) and R 14 Au 34+x Ga 17-x (Gd 14 Ag 51-type, space group P6/m, Z = 1, hP65) (R = Er, Tm), were synthesized by arc-melting, followed by annealing at 400-600ºC. Six phases RAu 1+x Ga 3-x (BaAl 4-type, space group I4/mmm, Z = 2, tI10) (R = Gd) and R 3 Au 3+x Ga 8-x (La 3 Al 11-type, space group Immm, Z = 2, oI26) (R = Tb-Tm) were prepared by the flux method. Their crystal structures were studied by X-ray powder or single crystal diffraction. Structural peculiarities, coordination and interaction of the atoms in the investigated compounds are briefly discussed. Rare-earth intermetallics / Ternary gallides / Crystal growth / Single crystal / X-ray diffraction / Crystal structure Experimental details Starting materials for the synthesis of the R-Au-Ga alloys were rare-earth ingots (R > 99.9 wt.%), gold plate (99.99 wt.%) and gallium pieces (99.999 wt.%). Samples with a total weight of 300 mg were prepared by arc-melting buttons in a water-cooled copper crucible with a tungsten electrode under a purified argon atmosphere, using Ti/Zr as a getter. The products were turned over and re-melted at least three times in order to ensure homogeneity. Fragments of

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Ferromagnetism and re-entrant spin-glass transition in quasicrystal approximants Au–SM–Gd (SM = Si, Ge)

Cited by 55 publications

References 18 publications

Magnetic and transport properties of i- R -Cd icosahedral quasicrystals (R=Y,Gd-Tm)

Magnetic and transport properties of i- R -Cd icosahedral quasicrystals (R=Y,Gd-Tm)

Long-range magnetic order in models for rare-earth quasicrystals

New ternary phases from the R–Au–Ga systems (R = Gd-Tm)

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