First- and second-order phase transitions in ternary europium phosphides with ThCr2Si2-type structure

Huhnt, C.; Schlabitz, W.; Wurth, A.; Mewis, A.; Reehuis, M.

doi:10.1016/s0921-4526(97)00904-6

Cited by 49 publications

(48 citation statements)

References 13 publications

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“…The common structural trend in AFe 2 As 2 compounds is a continuous decrease in the lattice parameter c and an anomalous increase in the parameter a with increasing pressure in the course of the isostructural transformation [19][20][21][22]. This resembles the second-order phase transition in compounds with the ThCr 2 Si 2 -structure [24]. Contrary to this, both lattice parameters a and c in TlFe 1.6 Se 2 decrease discontinuously at the pressure of the phase transition (Fig.…”

Section: Resultsmentioning

confidence: 86%

Pressure-induced magnetic collapse and metallization of TlFe1.6Se2

et al. 2017

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Abstract. The crystal structure, magnetic ordering, and electrical resistivity of TlFe 1.6 Se 2 were studied at high external pressures. Below ~7 GPa, TlFe 1.6 Se 2 is an antiferromagnetically ordered semiconductor with a ThCr 2 Si 2 -type structure. The insulator-to-metal transformation observed at a pressure of ~ 7 GPa is accompanied by a loss of magnetic ordering and an isostructural phase transition. In the pressure range ~ 7.5 -11 GPa a remarkable downturn in resistivity, which resembles a superconducting transition, is observed below 15 K. We discuss this feature as the possible onset of superconductivity originating from a phase separation in a small fraction of the sample in the vicinity of the magnetic transition.

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Section: Resultsmentioning

confidence: 86%

Pressure-induced magnetic collapse and metallization of TlFe1.6Se2

et al. 2017

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“…2 However, in contrast to EuCo 2 P 2 the pressure-induced structural ͑␣→␤͒ phase transition in EuFe 2 P 2 is continuous for 3 GPaрpр9 GPa. 12 Thus, the investigation of the influence of the pressure-induced structural phase transition on the electronic and magnetic properties of EuFe 2 P 2 in comparison with EuCo 2 P 2 should provide valuable information on the nature of strong electron correlations in these compounds. To obtain a theoretical interpretation of the experimental results, we have performed volume-dependent band-structure calculations on EuFe 2 P 2 and EuCo 2 P 2 .…”

Section: Johrendtmentioning

confidence: 99%

Interplay between structural, electronic, and magnetic instabilities inEuT2P2
Ni
¹
,
Abd‐Elmeguid
²
,
Micklitz
³

et al. 2001
Phys. Rev. B

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151 Eu ͑and 57 Fe) high-pressure Mössbauer investigations on EuFe 2 P 2 reveal that the pressure-induced isostructural phase transition 3ՇpՇ9 GPa is accompanied by a continuous valence transition from Eu 2ϩ to Eu 3ϩ with the consequence of the disappearance of the Eu͑4 f ) sublattice moment. However, contrary to EuCo 2 P 2 we find in the high-pressure phase of EuFe 2 P 2 no magnetic moment on Fe. Volume-dependent band-structure calculations in both systems show that the formation of the 3d moment strongly depends on the position of the 3d states relative to the Fermi energy and that the filling of the 3d states in EuCo 2 P 2 is mainly caused by the P-3p electrons.The rare-earth (RE) transition metal ͑T͒ phosphides, RET 2 P 2 , crystallizing in the ThCr 2 Si 2 -type structure belong to an interesting class of materials in which structural instability is intimately connected with electronic and magnetic instabilities. These strong electron correlations lead to the formation of a large variety of ground states in this series. Depending on the type of RE and/or T, one observes not only different magnetic phenomena such as 4 f -sublattice magnetism (EuCo 2 P 2 ), 1 3d-sublattice magnetism (LaCo 2 P 2 ) 2 or magnetism of both sublattices (PrCo 2 P 2 ), 3 but also intermediate valent behavior (EuNi 2 P 2 ) 4 or even superconductivity (LaRu 2 P 2 ). 5 Essentially responsible for such a broad variety of properties is the ability of the ThCr 2 Si 2 structure to adapt to several elements with various atomic sizes resulting in extremely different lattice parameters. In fact, within the RET 2 P 2 series, there exists two extremely dissimilar P-P distances along the c axis resulting in two isostructural phases: ␣ phase for a large P-P distance (d P-P Ϸ2.8 Å͒ with a nonbonding P-P state; and ␤ phase for a short d P-P Ϸ2.3 Å forming a P-P single bond state. 6 Structural phase transitions of first-and second-order between these phases can easily be induced by changing composition, 7 temperature, 8 or applying external pressure. 9 According to recent band-structure calculations on some RET 2 P 2 compounds such structural phase transitions strongly affect the electronic structure of these systems. 10 Towards understanding such an interplay in RET 2 P 2 systems, we have recently performed high-pressure experiments ( 151 Eu Mössbauer spectroscpopy and x-ray diffraction͒ on the magnetically ordered compound EuCo 2 P 2 . 11 In this system, antiferromagnetism is due to ordering of the Eu 2ϩ ͑ 8 S 7/2 ) sublattice moments (T N ϭ66.5 K͒ while the Co(3d) sublattice exhibits no magnetic moments. Here, high-pressure experiments demonstrated that the pressure-induced first-order structural ͑␣→␤͒ phase transition at pϾ3 GPa is connected with a sharp valence transition of Eu from magnetic Eu 2ϩ to a nonmagnetic Eu 3ϩ ( 7 F 0 ) state. As a consequence, the disappearance of the Eu(4 f ) sublattice magnetism is accompanied by a simultaneous appearance of Co(3d) sublattice magnetism with T N *ϭ260 K. 11 These experimental findings, however, rais...

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“…However, the cT phase transition is not unique to the AeFe 2 As 2 family and was predicted in compounds with the AB 2 X 2 (B = transition metal, X = group 14 or 15 element) structure in which the X -X contact varies over the range of bonding between no bond and a fully formed X -X single bond. 13 Indeed, the cT phase has been observed in many compounds with the ThCr 2 Si 2 structure [14][15][16][17] as well as in the recently discovered CaKFe 4 As 4 superconductor which may even host a two-step cT transition. 18 The electronic properties of the cT phase are vastly different than of the un-collapsed tetragonal (TET) phase due to the abrupt change of the electronic bandstructure, associated with the structural change 19 , e.g., the transition into the cT phase often leads to the loss of magnetism or SC.…”

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confidence: 99%

Collapsed tetragonal phase transition in LaRu2P2

et al. 2017

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The structural properties of LaRu2P2 under external pressure have been studied up to 14 GPa, employing high-energy x-ray diffraction in a diamond-anvil pressure cell. At ambient conditions, LaRu2P2 (I 4/mmm) has a tetragonal structure with a bulk modulus of B = 105(2) GPa and exhibits superconductivity at Tc = 4.1 K. With the application of pressure, LaRu2P2 undergoes a phase transition to a collapsed tetragonal (cT) state with a bulk modulus of B = 175(5) GPa. At the transition, the c-lattice parameter exhibits a sharp decrease with a concurrent increase of the a-lattice parameter. The cT phase transition in LaRu2P2 is consistent with a second order transition, and was found to be temperature dependent, increasing from P = 3.9(3) GPa at 160 K to P = 4.6(3) GPa at 300 K. In total, our data are consistent with the cT transition being near, but slightly above 2 GPa at 5 K where superconductivity is suppressed. Finally, we compare the effect of physical and chemical pressure in the RRu2P2 (R = Y, La-Er, Yb) isostructural series of compounds and find them to be analogous.

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First- and second-order phase transitions in ternary europium phosphides with ThCr2Si2-type structure

Cited by 49 publications

References 13 publications

Pressure-induced magnetic collapse and metallization of TlFe1.6Se2

Pressure-induced magnetic collapse and metallization of TlFe1.6Se2

Interplay between structural, electronic, and magnetic instabilities inEuT2P2
Ni
¹
,
Abd‐Elmeguid
²
,
Micklitz
³

et al. 2001
Phys. Rev. B

Collapsed tetragonal phase transition in LaRu2P2

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First- and second-order phase transitions in ternary europium phosphides with ThCr2Si2-type structure

Cited by 49 publications

References 13 publications

Pressure-induced magnetic collapse and metallization of TlFe1.6Se2

Pressure-induced magnetic collapse and metallization of TlFe1.6Se2

Interplay between structural, electronic, and magnetic instabilities inEuT2P2Ni1, Abd‐Elmeguid2, Micklitz3 et al. 2001Phys. Rev. B

Collapsed tetragonal phase transition in LaRu2P2

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Interplay between structural, electronic, and magnetic instabilities inEuT2P2
Ni
¹
,
Abd‐Elmeguid
²
,
Micklitz
³

et al. 2001
Phys. Rev. B