Valence and magnetic transitions in YbMn2Ge2—Pressure and temperature

Hofmann, M.; Campbell, S.J.; Link, P.; Fiddy, Steven G.; Goncharenko, I. N.

doi:10.1016/j.physb.2006.05.034

Cited by 8 publications

(16 citation statements)

References 5 publications

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“…The calculations find the intermediate valence state as the ground state through the entire pressure range, with a valence increase at a rate dv/dp ∼ 0.005 GPa −1 , that is, significantly slower than observed (inset to Figure 3). The significant change in average valence observed around 1.4 GPa is in excellent agreement with the high pressure neutron diffraction experiments, 12,13 which observe a 7% collapse in the specific volume between 1.0 and 1.5 GPa. Similar volume collapses occur for the Yb chalcogenides 14−16 and indicate a change in 4f occupancy.…”

Section: Resultssupporting

confidence: 87%

“…The transition pressure for this magnetic structural change is calculated to be 1.2 GPa, a number coinciding with the experimental magnetic transition pressure of 1.25 GPa. 13,19,20 However, this agreement is likely to be somewhat fortuitous, since the SIC-LSD theory includes some inaccuracies, for example, with respect to calculated equilibrium volumes.…”

Section: Resultsmentioning

confidence: 98%

“…1−4 In Yb compounds the Yb ions may be found either in the 4f 13 (3+) or the 4f 14 (2+) configuration. The energy difference between these two valence states is in many cases small, and therefore rapid configurational changes can be induced by small changes in temperature, pressure, or magnetic field.…”

Section: Introductionmentioning

confidence: 99%

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Pressure-Induced Valence and Structural Changes in YbMn₂Ge₂—Inelastic X-ray Spectroscopy and Theoretical Investigations

et al. 2013

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The pressure-induced valence change of Yb in YbMn(2)Ge(2) has been studied by high pressure inelastic X-ray emission and absorption spectroscopy in the partial fluorescence yield mode up to 30 GPa. The crystal structure of YbMn(2)Ge(2) has been investigated by high pressure powder X-ray diffraction experiments up to 40 GPa. The experimental investigations have been complemented by first principles density functional theoretical calculations using the generalized gradient approximation with an evolutionary algorithm for structural determination. The Yb valence and magnetic structures have been calculated using the self-interaction corrected local spin density approximation. The X-ray emission results indicate a sharp increase of Yb valence from v = 2.42(2) to v = 2.75(3) around 1.35 GPa, and Yb reaches a near trivalent state (v = 2.95(3)) around 30 GPa. Further, a new monoclinic P1 type high pressure phase is found above 35 GPa; this structure is characterized by the Mn layer of the ambient (I4/mmm) structure transforming into a double layer. The theoretical calculations yield an effective valence of v = 2.48 at ambient pressure in agreement with experiment, although the pure trivalent state is attained theoretically at significantly higher pressures (above 40 GPa).

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 98%

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Pressure-Induced Valence and Structural Changes in YbMn₂Ge₂—Inelastic X-ray Spectroscopy and Theoretical Investigations

et al. 2013

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“…1 [11,12]. In the latter phases, the valence of Yb is significantly lower ( $ 2:5) and the transition metal sublattice is either weakly magnetized [11] or antiferromagnetically arranged [12].…”

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confidence: 99%

“…Our model well describes the behavior recently reported for Although our simplified model seems able to capture the essential physics, it cannot be excluded that the high sensitivity of the Yb valence vis-à-vis the lattice contraction in these alloys might also participate in the anomalous temperature variation of the Yb valence. In Yb-based systems, the increase in the external [11,12,23] or chemical pressure [24], which reduces the interatomic distances, favors the trivalent state due to the smaller radius of trivalent Yb compared with that of divalent Yb. With Yb valence around $ 2:9, as in the present cases, a significant valence variation requires a $10 GPa pressure corresponding to a $10% volume reduction [23,25].…”

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confidence: 99%