Electronic Structure and Nesting-Driven Enhancement of the RKKY Interaction at the Magnetic Ordering Propagation Vector inGd2PdSi3andTb2PdSi3

Abstract

We present first-time measurements of the Fermi surface and low-energy electronic structure of intermetallic compounds Gd 2 PdSi 3 and Tb 2 PdSi 3 by means of angle-resolved photoelectron spectroscopy (ARPES). Both materials possess a flower-like Fermi surface consisting of an electron barrel at the Γ point surrounded by spindle-shaped electron pockets originating from the same band. The band bottom of both features lies at 0.5 eV below the Fermi level. From the experimentally measured band structure, we estimate the momentum-dependent RKKY coupling strength and demonstrate that it is peaked at the 1 2 ΓK wave vector. Comparison with neutron diffraction data from the same crystals shows perfect agreement of this vector with the propagation vector of the low-temperature in-plane magnetic order, thereby demonstrating the decisive role of the Fermi surface geometry in explaining the complex magnetically ordered ground state of ternary rare earth silicides. Ternary rare earth silicides with hexagonal crystal structure of the form R 2 PdSi 3 , where R is a rare earth atom, are known to exhibit complex magnetic behavior [1,2,3,4,5,6,7,8,9,10,11,12,13,14] Most of the R 2 PdSi 3 compounds order magnetically at low temperatures, somewhat below the Kondo minimum in the resistivity [2,3,4,5,6]. The exact type of such ordering strongly depends on the material and can be rather complicated [6,10]. The corresponding Neel temperature T N reaches maximum for the Gd (T N =21.0 K [11]) and Tb (T N =23.6 K [12]) compounds, which we have chosen as the subject of the present study. The RKKY exchange interaction that essentially determines their magnetic properties is mediated by the conductance electrons, and therefore any reasonable description of the corresponding physics is impossible without the knowledge of the Fermi surface and the low-energy electronic structure. According to our recent study [16], the sign reversal of the Hall effect observed at low temperatures in R 2 PdSi 3 [13] might be an indication of the opening of the pseudogap at some portions of the Fermi surface, as was also suggested earlier by resistivity measurements [2], again emphasizing the importance of studying the electronic structure of these materials.Nevertheless, though the single crystals of Gd 2 PdSi 3 are available since nearly a decade [3], the fermiology and the underlying band structure are still not known for any of the R 2 PdSi 3 compounds neither from momentum-resolved measurements nor from band structure calculations. Earlier photoemission experiments [17,18] were performed only on polycrystalline samples and could not therefore shed light on the dispersion of conductance electrons and the Fermi surface geometry, but have revealed that the density of states at the Fermi level is likely to be dominated by the 5d states of the rare earth atoms.Here we report an angle-resolved photoelectron spectroscopy (ARPES) investigation of the low-energy electronic structure performed on the single crystals of Gd 2 PdSi 3 and Tb 2 PdSi 3 , whose crystal st...

Crystallographic superstructure inR2PdSi3compounds (R=heavyrare earth)

“…With the availability of large high-quality single crystals 30-32 more detailed studies have been performed on the series of compounds to clarify the magnetic properties as well as the crystal structure. 27,[33][34][35][36] In R 2 PdSi 3 single crystals, weak additional reflections were observed by x-ray diffraction 37 and neutron scattering 27 with no structural phase transition between room and very low temperatures (down to 1.5 K). Furthermore, a systematic study on the single crystals with ac susceptibility, magnetization measurements, and neutron scattering revealed a generic phase in the field-temperature phase diagram in this series.…”

Doping-induced redistribution of magnetic spectral weight in the substituted hexaborides Ce1−xLaxB6 and Nikitin1, Portnichenko2, Dukhnenko3 et al. 2018Phys. Rev. BSelf Cite123160View full textAdd to dashboardCite

“…* Corresponding author: Dmytro.Inosov@tu-dresden. de A handful of earlier works on magnetic heavy-fermion metals, where conduction electrons are involved in the formation of magnetic order, suggest that the low-energy dynamic spin susceptibility χ(ω, Q), measured with diffuse neutron scattering, provides direct information about the nesting vectors [7][8][9][10][11][12][13][14][15][16]. Due to the bulk sensitivity of neutron scattering, it therefore serves as a complementary method for probing the 3D electronic structure.…”

“…This limits its applicability to materials with highly 3-dimensional (3D) band structures. Extraction of Fermisurface nesting vectors from ARPES data is possible and has been successful in many earlier works [1][2][3][4][5][6][7][8], but it usually relies on a technically demanding fit of the whole low-energy band structure to a tight-binding model with a consequent momentum integration to extract the peaks in a two-particle correlation function. This method is, therefore, indirect.…”

Incommensurate antiferromagnetism in a pure spin system via cooperative organization of local and itinerant moments

“…Studying the spin behavior in Gd compounds via neutron scattering is difficult due to the large neutron absorption cross-section of the most common isotope. However, long-range incommensurate spin ordering was revealed by X-ray magnetic diffraction in several Gd compounds such as GdCo 2 Ge 2 , GdNi 2 Ge 2 , and GdNi 2 B 2 C (6,7,19), and the idea of cooperative RKKY and nesting effects was discussed in systems such as GdNi 2 Ge 2 (19) and Tb 2 PdSi 3 (20). However, for GdNi 2 Ge 2 and GdNi 2 B 2 C, lack of a resistance anomaly at the onset of magnetic ordering suggests that the incommensurate spin structure is not likely to involve any gapping of the Fermi surface (21,22), and for Tb 2 PdSi 3 it is unclear whether resolution-limited, longrange magnetic order exists at the wave vector suggested by the angle-resolved photoemission spectroscopy (ARPES) work (20).…”