Rare-earth Intermetallics Research Articles

Field induced metamagnetism and large magnetic entropy change in RRhSi (R = Tb, Dy, Ho) rare earth intermetallics

We report magnetic, magneto-caloric, electronic structure, and optical properties of rare earth intermetallics RRhSi (R=Tb, Dy, Ho). These compounds show antiferromagnetic ordering at low temperatures. The magnetization data reveal field-induced metamagnetic transition in DyRhSi and HoRhSi compounds, which results in large magnetocaloric effect (MCE) in these compounds. In the case of Dy, the MCE is found to be larger than those of other analogs of the RTX family. Theoretical calculations confirm antiferromagnetic ordering in these compounds and show a negligible contribution of magnetic moment from Rh atom. The optical measurements carried out for these materials support the theoretical calculations. We uncover large magnetocaloric effect in DyRhSi and HoRhSi intermetallics attributed to metamagnetic transition and identify electronic states involved in the formation of magnetic and spectral properties based on DFT+U and optical studies.

Bandwidth-control orbital-selective delocalization of 4f electrons in epitaxial Ce films

The 4f-electron delocalization plays a key role in the low-temperature properties of rare-earth metals and intermetallics, and it is normally realized by the Kondo coupling between 4f and conduction electrons. Due to the large Coulomb repulsion of 4f electrons, the bandwidth-control Mott-type delocalization, commonly observed in d-electron systems, is difficult in 4f-electron systems and remains elusive in spectroscopic experiments. Here we demonstrate that the bandwidth-control orbital-selective delocalization of 4f electrons can be realized in epitaxial Ce films by thermal annealing, which results in a metastable surface phase with reduced layer spacing. The quasiparticle bands exhibit large dispersion with exclusive 4f character near bar{{{Gamma }}} and extend reasonably far below the Fermi energy, which can be explained from the Mott physics. The experimental quasiparticle dispersion agrees well with density-functional theory calculation and also exhibits unusual temperature dependence, which could arise from the delicate interplay between the bandwidth-control Mott physics and the coexisting Kondo hybridization. Our work opens up the opportunity to study the interaction between two well-known localization-delocalization mechanisms in correlation physics, i.e., Kondo vs Mott, which can be important for a fundamental understanding of 4f-electron systems.

Structural and Physical Properties of DyCu, NdAg, LaCd, YIn, ErCu, ErAg, and ErAu Rare-Earth Intermetallic Compounds: Ab initio Investigations Analyzed by Data Mining Technique

In this work, the structural, elastic, mechanical, thermodynamic, and electronic properties of ErCu, ErAg, ErAu, DyCu, NdAg, LaCd, and YIn compounds have been investigated systematically using full-potential linearized augmented plane wave (FP-LAPW) within the density functional theory (DFT). In this approach, the exchange–correlation energy was calculated with generalized gradient approximation (GGA), by Perdew–Burke–Ernzerhof (PBE). We have firstly calculated lattice constants, bulk modulus, elastic constants, and mechanical properties such as Young’s and shear moduli, Pugh factor (B/G), anisotropy constant, and Cauchy pressure, as well as Poisson coefficient. The elastic constants and their related properties verify the criteria of mechanical stability, signifying that these compounds are stable in B2 structure. The ductility of the intermetallics investigated here is evaluated. The obtained values show that ErCu is the most rigid while NdAg the most ductile. The total and partial electron density of states (DOS) were evaluated to offer a detailed explanation of the contribution of atomic orbitals in the energy bands. The thermodynamic properties of ErCu, ErAg, ErAu, NdAg, LaCd, YIn, and DyCu are calculated via the quasi-harmonic Debye model, in which the lattice vibrations are considered. So temperature-dependent parameters such as lattice constant, thermal expansion, and specific heat at constant volume are analyzed. Furthermore, the relationship between several thermo-physical and mechanical properties was discussed and analyzed with data mining techniques. The obtained results confirm that this B2-type of rare-earth intermetallics has very interesting mechanical and thermal properties for structural applications.

Martensitic αʺ-Fe16N2-Type Phase of Non-Stoichiometric Composition: Current Status of Research and Microscopic Statistical-Thermodynamic Model

The literature (experimental and theoretical) data on the tetragonality of martensite with interstitial–substitutional alloying elements and vacancies are reviewed and analysed. Special attention is paid to the studying the martensitic αʺ-Fe16N2-type phase with unique and promising magnetic properties as an alternative to the rare-earth intermetallics or permendur on the world market of the production of permanent magnets. The period since its discovery to the current status of research is covered. A statistical-thermodynamic model of ‘hybrid’ interstitial–substitutional solid solution based on a b.c.t. crystal lattice, where the alloying non-metal constituents (impurity atoms) can occupy both interstices and vacant sites of the host b.c.c.(t.)-lattice, is elaborated. The discrete (atomic-crystalline) lattice structure, the anisotropy of elasticity, and the ‘blocking’ and strain-induced (including ‘size’) effects in the interatomic interactions are taken into account. The model is adapted for the non-stoichiometric phase of Fe–N martensite maximally ordered by analogy with αʺ-Fe16N2, where nitrogen atoms are in the interstices and at the sites of b.c.t. iron above the Curie point. It is stressed an importance of adequate data on the available (in the literature) temperature- and concentration-dependent microscopic energy parameters of the interactions of atoms and vacancies. The features of varying (viz. non-monotonic decreasing with increasing temperature) the relative concentration of N atoms in the octahedral interstices of b.c.t. Fe, and therefore, the degree of its tetragonality (correlating with this concentration) are elucidated. Within the wide range of varying the total content of introduced N atoms, the ratio of the equilibrium concentration of residual site vacancies to the concentration of thermally activated vacancies in a pure b.c.c. Fe is demonstrated at a fixed temperature.

Exploring the Different Degrees of Magnetic Disorder in TbxR1-xCu2 Nanoparticle Alloys.

Recently, potential technological interest has been revealed for the production of magnetocaloric alloys using Rare-Earth intermetallics. In this work, three series of TbRCu (R ≡ Gd, La, Y) alloys have been produced in bulk and nanoparticle sizes via arc melting and high energy ball milling. Rietveld refinements of the X-ray and Neutron diffraction patterns indicate that the crystalline structure in all alloys is consistent with TbCu orthorhombic bulk crystalline structure. The analyses of the DC-magnetisation () and AC-susceptibility () show that three distinct degrees of disorder have been achieved by the combination of both the Tb replacement (dilution) and the nanoscaling. These disordered states are characterised by transitions which are evident to , and specific heat. There exists an evolution from the most ordered Superantiferromagnetic arrangement of the TbLaCu NPs with Néel temperature, 27 K, and freezing temperature, 7 K, to the less ordered weakly interacting Superparamagnetism of the TbYCu nanoparticles ( absent, and T 3 K). The Super Spin Glass TbGdCu nanoparticles ( absent, and 20 K) are considered an intermediate disposition in between those two extremes, according to their enhanced random-bond contribution to frustration.

Investigation of the Field-Induced Phase Transitions in the (R,R′)2Fe14B Rare-Earth Intermetallics in Ultrahigh Magnetic Fields

In this work, we perform a comparative study of the magnetization behavior of four series of compounds R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sub> B and their hydrides R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sub> BH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5.5</sub> , and the compositions (Nd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> ) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sub> B and their hydrides (Nd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> ') <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sub> BH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5.5</sub> with R and R' = Ho, Er, and Tm. The magnetization is measured in pulsed magnetic fields up to 58 T and in megagauss fields up to 135 T at 5 K. The first and second critical fields of the field-induced transitions, H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c1</sub> and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c2</sub> were estimated analytically and the results were verified against experimental data. We find that hydrogenation of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sub> B and (Nd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> ') <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sub> B reduces drastically the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c1</sub> and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c2</sub> values and, as a consequence, the intersublattice R-Fe exchange interaction parameter λ.

A novel ultra-high temperature Pt–Rh alloy with balanced tensile strength and creep resistance achieved by rare-earth intermetallics

A novel ultra-high temperature Pt–25Rh (wt.%) alloy with a minor addition of rare-earth (RE) elements (0.2 wt% La and 0.2 wt% Ce) was developed for the first time which exhibits the capability to withstand aggressive environment with a high operating temperature of >1500 °C. Tensile creep tests of the alloy were carried out at 1500 °C under a load of 5 MPa, the high tensile strength (σb) was up to 47.8 MPa, the creep rate (ε) as low as 0.008%/h and a rupture time (τ) more than 53 h, respectively. Detailed microstructure characterization revealed that there exist two balanced phases in the alloy, a ductile (Pt, Rh) solid solution phase with a face-centered cubic structure and a strengthening Pt5RE (RE = La, Ce) intermetallic phase with a hexagonal structure. The Pt5RE phases present three types of forms in the alloy, precipitates in the (Pt, Rh)ss matrix, an intergranular phase along the grain boundaries and a eutectic mixture in the matrix. Composition analysis showed that RE elements almost completely exist in the Pt5RE intermetallic phase but rarely in the (Pt, Rh)ss phase. It is interesting to note that the Pt5RE intermetallic phase is a RE-poor phase in which the content of RE elements is less than 5 wt%, much lower than the stoichiometric ratio (12.46 wt%). Compared with the reported Pt–Rh binary alloys, a minor additions of La and Ce in the new alloy effectively improves its high-temperature mechanical properties, which can be attributed to the formation of the strengthening Pt5RE intermetallic phase. By the way, an orientation relationship was identified between the Pt5RE and (Pt, Rh)ss phases in the eutectic structure for the first time.

Nanometric square skyrmion lattice in a centrosymmetric tetragonal magnet.

Magnetic skyrmions are topologically stable spin swirls with a particle-like character and are potentially suitable for the design of high-density information bits. Although most known skyrmion systems arise in non-centrosymmetric systems with a Dzyaloshinskii-Moriya interaction, centrosymmetric magnets with a triangular lattice can also give rise to skyrmion formation, with a geometrically frustrated lattice being considered essential in this case. Until now, it remains an open question if skyrmions can also exist in the absence of both geometrically frustrated lattice and inversion symmetry breaking. Here we discover a square skyrmion lattice state with 1.9 nm diameter skyrmions in the centrosymmetric tetragonal magnet GdRu2Si2 without a geometrically frustrated lattice by means of resonant X-ray scattering and Lorentz transmission electron microscopy experiments. A plausible origin of the observed skyrmion formation is four-spin interactions mediated by itinerant electrons in the presence of easy-axis anisotropy. Our results suggest that rare-earth intermetallics with highly symmetric crystal lattices may ubiquitously host nanometric skyrmions of exotic origins.

Anisotropic electrical and thermal magnetotransport in the magnetic semimetal GdPtBi

The half-Heusler rare-earth intermetallic GdPtBi has recently gained attention due to peculiar magnetotransport phenomena that have been associated with the possible existence of Weyl fermions, thought to arise from the crossings of spin-split conduction and valence bands. On the other hand, similar magnetotransport phenomena observed in other rare-earth intermetallics have often been attributed to the interaction of itinerant carriers with localized magnetic moments stemming from the $4f$-shell of the rare-earth element. In order to address the origin of the magnetotransport phenomena in GdPtBi, we performed a comprehensive study of the magnetization, electrical and thermal magnetoresistivity on two single-crystalline GdPtBi samples. In addition, we performed an analysis of the Fermi surface via Shubnikov-de Haas oscillations in one of the samples and compared the results to \emph{ab initio} band structure calculations. Our findings indicate that the electrical and thermal magnetotransport in GdPtBi cannot be solely explained by Weyl physics and is strongly influenced by the interaction of both itinerant charge carriers and phonons with localized magnetic Gd-ions and possibly also paramagnetic impurities.

Possible room-temperature signatures of unconventional 4f -electron quantum criticality in YbMn6Ge6−xSnx

We investigate the Sn composition dependence of the Yb valence and local magnetization in ${\mathrm{YbMn}}_{6}{\mathrm{Ge}}_{6\ensuremath{-}x}{\mathrm{Sn}}_{x}$ ($4.25\ensuremath{\le}x\ensuremath{\le}5.80$) using x-ray absorption spectroscopy (XANES) and x-ray magnetic circular dichroism at the Yb ${L}_{3}$ edge. In these materials, where Mn is ferromagnetically ordered, we observe a decrease of the Yb valence upon reducing the chemical pressure by Sn doping and a suppression of the Yb magnetic moment for strongly hybridized $4f$ states ($\ensuremath{\nu}\ensuremath{\sim}2.77$). In the vicinity of the Yb magnetic instability (${x}_{c}\ensuremath{\sim}5.23$), a remarkably sharp peak is observed in the composition dependence of the valence and magnetic moment at low temperature, which is reminiscent of enhanced valence and magnetic susceptibilities predicted by recent theories on unconventional quantum criticality. This anomaly is also present in the room-temperature XANES signal, suggesting that rare-earth intermetallics with a magnetized $3d$ sublattice form a distinct group of heavy-fermion metals where the high energy of the exchange interactions can bring quantum criticality up to high temperature.

Electronic structure of the parent compound of superconducting infinite-layer nickelates.

The search continues for nickel oxide-based materials with electronic properties similar to cuprate high-temperature superconductors1-10. The recent discovery of superconductivity in the doped infinite-layer nickelate NdNiO2 (refs. 11,12) has strengthened these efforts. Here, we use X-ray spectroscopy and density functional theory to show that the electronic structure of LaNiO2 and NdNiO2, while similar to the cuprates, includes significant distinctions. Unlike cuprates, the rare-earth spacer layer in the infinite-layer nickelate supports a weakly interacting three-dimensional 5d metallic state, which hybridizes with a quasi-two-dimensional, strongly correlated state with [Formula: see text] symmetry in the NiO2 layers. Thus, the infinite-layer nickelate can be regarded as a sibling of the rare-earth intermetallics13-15, which are well known for heavy fermion behaviour, where the NiO2 correlated layers play an analogous role to the 4f states in rare-earth heavy fermion compounds. This Kondo- or Anderson-lattice-like 'oxide-intermetallic' replaces the Mott insulator as the reference state from which superconductivity emerges upon doping.

Enhanced magnetocaloric effect in undercooled rare earth intermetallic compounds RNi (R = Gd, Ho and Er)

Equiatomic RNi (where R = Gd, Ho and Er) compounds have been prepared by undercooling. Magnetization data confirm ferromagnetic ordering of the samples at 69 K, 35 K and 10 K (TC) respectively. Magnetocaloric effect (MCE) has been estimated in terms of isothermal magnetic entropy change (ΔSm) near TC. The maximum ΔSm value (ΔSmmax) for 50 kOe field change is about −18 Jkg-1K−1, −20 Jkg-1K−1 and −30 Jkg-1K−1 respectively near TC for the undercooled RNi (R = Gd, Ho and Er) compounds. The ΔSmmax value is more than that obtained for the same compounds prepared by arc-melting and melt-spinning techniques. The observed enhancement in MCE of the undercooled samples could be due to the improved purity that results in faster change of magnetization around the magnetic transition. Thus undercooling rare earth intermetallics and alloys seems to be an attractive, alternative method to synthesize magnetocaloric materials.

Spin-glass features at multiple temperatures and transport anomalies in Tb4PtAl

The magnetic and electrical transport properties of Tb4PtAl, crystallizing in the Gd4RhIn-type cubic crystal structure characterized by three sites for the rare-earth, are reported by the measurements of magnetization, heat-capacity, and electrical resistivity (1.8–300 K). In comparison with the Gd analog, which has been shown to exhibit a complex magnetism with antiferromagnetism (TN = 64 K) entering into a spin-glass phase below 20 K, the spin-glass phase coexists at the onset of the antiferromagnetic order at 50 K in the Tb compound; additional spin-glass anomalies around 8 and 25 K are also found. Interestingly, the plot of electrical resistivity vs temperature develops a minimum in the presence of an external magnetic field above 50 K, and this transport behavior, unusual among rare-earth intermetallics, is presumably due to the gradual growth of short-range antiferromagnetic clusters as the long-range magnetic order develops.

Physical properties and possible applications of gold-based rare earth intermetallics (R-Au): A review

Abstract This article explores, research and developments of various physical properties such as structural, thermal, magnetic , elastic, thermodynamic and thermoelectric of cubic rare-earth-gold equiatomic R-Au intermetallics (R= Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) of CsCl structure. These materials have the highest melting points and are also very hard among the known lanthanide intermetallics. The purpose of this review is to shed light on the physical properties of these least studied materials and also encourage researchers to evaluate them for their possible high-tech applications. Furthermore, this study will provide reference data for the future experimental / theoretical work on these intermetallics and will help in identifying the gaps in the current status of knowledge about these compounds.

Effect of Rare Earth Metals on the Mechanical Properties and Fractography of Al–Si-Based Alloys

The present study was performed on A356 and A413 alloys in non-modified and Sr-modified conditions. To these alloys, pure rare earth (RE) metals, mainly lanthanum (La) and cerium (Ce), were added in the amount of 1 wt% each, individually or combined. The results showed that the addition of 2% RE leads to a significant reduction in the grain size (~ 60%) compared to the base alloy. However, it also leads to precipitation of a large amount of insoluble intermetallics (~ 10% in volume fraction). These intermetallics cause a significant decrease in the alloy ductility and hence deteriorate the tensile properties and impact energies. In addition, Sr may also cause destabilization of the RE intermetallics with possibility of partial dissolution during solution heat treatment. The RE metals have an affinity to react with Sr leading to partial demodification of the eutectic Si. They also react with Cu, diminishing the alloy response to age hardening. The RE intermetallics act as crack initiation sites, leading to premature failure of the sample. The combined occurrence of these various effects complicates the prediction of the alloy behavior.

New ternary aluminides RERh4Al15 (RE = La, Ce, Pr, Sm, Gd)

The aluminum-rich intermetallic rare earth compounds RERh4Al15 (RE = La, Ce Pr, Sm, Gd) were synthesized by arc melting of the elements under an argon atmosphere. The samples were characterized by powder X-ray diffraction which revealed a straight-forward agreement of the synthesized materials with tetragonal space group P42/nmc, NdRh4Al15.37 structure type. The structures of CeRh4Al15 and PrRh4Al15 were refined from single-crystal X-ray diffraction data. CeRh4Al15 is a new correlated electron compound with Kondo interaction. There is no magnetic ordering above 0.05 K despite the localized Ce3+ magnetic moment behaviour near room temperature. The electronic specific heat, magnetic susceptibility and electrical resistivity indicate that the compound may be accidently poised near a magnetic quantum critical point.

Why rare-earth ferromagnets are so rare: Insights from the p -wave Kondo model

Magnetic exchange in Kondo lattice systems is of the Ruderman-Kittel-Kasuya-Yosida type, whose sign depends on the Fermi wave vector, $k_F$ . In the simplest setting, for small $k_F$ , the interaction is predominately ferromagnetic, whereas it turns more antiferromagnetic with growing $k_F$. It is remarkable that even though $k_F$ varies vastly among the rare-earth systems, an overwhelming majority of lanthanide magnets are in fact antiferromagnets. To address this puzzle, we investigate the effects of a p-wave form factor for the Kondo coupling pertinent to nearly all rare-earth intermetallics. We show that this leads to interference effects which for small kF are destructive, greatly reducing the size of the RKKY interaction in the cases where ferromagnetism would otherwise be strongest. By contrast, for large $k_F$, constructive interference can enhance antiferromagnetic exchange. Based on this, we propose a new route for designing ferromagnetic rare-earth magnets.

Phase transition of intermetallic TbPt at high temperature and high pressure

Here we present synchrotron-based x-ray diffraction experiments combined with diamond anvil cell and laser heating techniques on the intermetallic rare earth compound TbPt (Pnma and Z = 4) up to 32.5 GPa and ~1800 K. The lattice parameters of TbPt exhibit continuous compression behavior up to 18.2 GPa without any evidence of phase transformation. Pressure–volume data were fitted to a third-order Birch–Murnaghan equation of state with V0 = 175.5(2) Å3, = 110(5) GPa and = 3.8(7). TbPt exhibits anisotropic compression with βa > βb > βc and the ratio of axial compressibility is 2.50:1.26:1.00. A new monoclinic phase of TbPt assigned to the Pc or P2/c space group was observed at 32.5 GPa after laser heating at ~1800 K. This new phase is stable at high pressure and presented a quenchable property on decompression to ambient conditions. The pressure–volume relationship is well described by the second-order Birch–Murnaghan equation of state, which yields V0 = 672(4) Å3, = 123(6) GPa, which is about ~14% more compressible than the orthorhombic TbPt. Our results provide more information on the structure and elastic property view, and thus a better understanding of the physical properties related to magnetic structure in some intermetallic rare earth alloys.

Two-stage multipolar ordering in PrT2Al20 Kondo materials

Among heavy fermion materials, there is a set of rare-earth intermetallics with non-Kramers Pr$^{3+}$ $4f^2$ moments which exhibit a rich phase diagram with intertwined quadrupolar orders, superconductivity, and non-Fermi liquid behavior. However, more subtle broken symmetries such as multipolar orders in these Kondo materials remain poorly studied. Here, we argue that multi-spin interactions between local moments beyond the conventional two-spin exchange must play an important role in Kondo materials near the ordered to heavy Fermi liquid transition. We show that this drives a plethora of phases with coexisting multipolar orders and multiple thermal phase transitions, providing a natural framework for interpreting experiments on the Pr(TM)$_2$Al$_{20}$ class of compounds.

Tracing crystal-field splittings in the rare-earth-based intermetallic CeIrIn5

Crystal electric field states in rare earth intermetallics show an intricate entanglement with the many-body physics that occurs in these systems and that is known to lead to a plethora of electronic phases. Here, we attempt to trace different contributions to the crystal electric field (CEF) splittings in CeIrIn$_5$, a heavy-fermion compound and member of the Ce$M$In$_5$ ($M$= Co, Rh, Ir) family. To this end, we utilize high-resolution resonant angle-resolved photoemission spectroscopy (ARPES) and present a spectroscopic study of the electronic structure of this unconventional superconductor over a wide temperature range. As a result, we show how ARPES can be used in combination with thermodynamic measurements or neutron scattering to disentangle different contributions to the CEF splitting in rare earth intermetallics. We also find that the hybridization is stronger in CeIrIn$_5$ than CeCoIn$_5$ and the effects of the hybridization on the Fermi volume increase is much smaller than predicted. By providing the first experimental evidence for $4f_{7/2}^{1}$ splittings which, in CeIrIn$_5$, split the octet into four doublets, we clearly demonstrate the many-body origin of the so-called $4f_{7/2}^{1}$ state.