High-pressure X-ray diffraction study of UMn2Ge2

Siruguri, V.; Paranjpe, S. K.; Raj, P.; Sathyamoorthy, A.; Itié, J. P.; Polian, A.

doi:10.1016/j.physb.2003.09.267

Cited by 8 publications

(10 citation statements)

References 17 publications

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“…The full lines represent linear fits to the present data; the dashed lines indicate the values a crit1 = 4.06 Å and a crit2 = 4.02 Å as discussed in the text. (c) The calculated chemical pressure based on the values of B 0 = 73.5 GPa and

{B^{'}}_{0}

= 11:4 for UMn 2 Ge 2 as a function of Y content. The full line is a guide to the eye.…”

Section: Resultsmentioning

confidence: 99%

“…With respect to PrMn 2 Ge 2 as the reference, we consider the influence of the reduction in unit cell volume due to Y substitution to be analogous to the effects of “chemical pressure.” The Murnaghan equation of state and the experimental unit cell volumes of Pr 1− x Y x Mn 2 Ge 2 can be used to derive the related “chemical pressure.” It is accepted that the Murnaghan equation can be described as

P (V) = \frac{B_{0}}{{B^{'}}_{0}} ({(\frac{V_{0}}{V})}^{{B^{'}}_{0}} - 1),

where B 0 is the isothermal bulk modulus,

{B^{'}}_{0}

is its pressure derivative, and V 0 and V are the volumes at ambient pressure and pressure p , respectively. Using the values of B 0 = 73.5 GPa and

{B^{'}}_{0} = 11.4

from the closely related compound UMn 2 Ge 2 , the equivalent “chemical pressure” from Pr 1− x Y x Mn 2 Ge 2 compounds can be derived as shown in Fig. c.…”

Section: Resultsmentioning

confidence: 99%

“…The corresponding chemical pressure changes from ∼12.6 kbar for x = 0.4 to ∼50.7 kbar for x = 0.8, leading to a rate of change

d T_{normalN}^{inter}

/d p = 4.5 K kbar −1 compared with the rate of change in transition temperature with external pressure of

d T_{normalN}^{inter}

/d p = 22.2 K kbar −1 in Pr 0.5 Y 0.5 Mn 2 Ge 2 . Estimation of the value of chemical pressure due to Y substitution for Pr using the isothermal bulk modulus B 0 and its pressure derivative

{B^{'}}_{0}

of UMn 2 Ge 2 is expected to include additional uncertainty because the magnetic states change with pressure from F mc to AF mc (see ) and different magnetic states are expected to have different B 0 and

{B^{'}}_{0}

. Given this additional uncertainty, we think the comparison for

d T_{normalN}^{inter}

/d p is consistent with change in

T_{normalC}^{Pr}

, as discussed in where we noted the rate of change with mechanical pressure exceeds the change with chemical pressure by a factor of ∼2.…”

Section: Resultsmentioning

confidence: 99%

See 2 more Smart Citations

Magnetic transitions and the magnetocaloric effect in the Pr_1−xY_xMn₂Ge₂ system

Wang

Campbell

Din

et al. 2014

Physica Status Solidi (a)

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Layered rare earth compounds in the RMn2X2 series (R = rare‐earth; X = Ge, Si) are of interest for potential cooling applications at lower temperatures as they enable the structural and magnetic behavior to be controlled via substitution of R, Mn, and X atoms on the 2a, 4d, and 4e sites respectively. We continue investigations of the Pr1−xYxMn2Ge2 magnetic phase diagram as functions of both composition and Mn–Mn spacing using X‐ray and neutron diffraction, magnetization and differential scanning calorimetry measurements. Pr1−xYxMn2Ge2 exhibits an extended region of re‐entrant ferromagnetism around x ∼ 0.5 with re‐entrant ferromagnetism at TnormalcPr∼50 K for Pr0.5Y0.5Mn2Ge2. The entropy values −ΔSM around the ferromagnetic transition temperatures TnormalCinter from the layered antiferromagnetic AFl structure to the canted ferromagnetic structure Fmc (typically TnormalCinter∼330–340 K) have been derived for Pr1−xYxMn2Ge2 with x = 0.0, 0.2, and 0.5 for ΔB = 0–5 T. The changes in magnetic states due to Y substitution for Pr are discussed in terms of chemical pressure, external pressure, and electronic effects.

show abstract

{B^{'}}_{0}

= 11:4 for UMn 2 Ge 2 as a function of Y content. The full line is a guide to the eye.…”

Section: Resultsmentioning

confidence: 99%

P (V) = \frac{B_{0}}{{B^{'}}_{0}} ({(\frac{V_{0}}{V})}^{{B^{'}}_{0}} - 1),

where B 0 is the isothermal bulk modulus,

{B^{'}}_{0}

is its pressure derivative, and V 0 and V are the volumes at ambient pressure and pressure p , respectively. Using the values of B 0 = 73.5 GPa and

{B^{'}}_{0} = 11.4

from the closely related compound UMn 2 Ge 2 , the equivalent “chemical pressure” from Pr 1− x Y x Mn 2 Ge 2 compounds can be derived as shown in Fig. c.…”

Section: Resultsmentioning

confidence: 99%

“…The corresponding chemical pressure changes from ∼12.6 kbar for x = 0.4 to ∼50.7 kbar for x = 0.8, leading to a rate of change

d T_{normalN}^{inter}

/d p = 4.5 K kbar −1 compared with the rate of change in transition temperature with external pressure of

d T_{normalN}^{inter}

/d p = 22.2 K kbar −1 in Pr 0.5 Y 0.5 Mn 2 Ge 2 . Estimation of the value of chemical pressure due to Y substitution for Pr using the isothermal bulk modulus B 0 and its pressure derivative

{B^{'}}_{0}

{B^{'}}_{0}

. Given this additional uncertainty, we think the comparison for

d T_{normalN}^{inter}

/d p is consistent with change in

T_{normalC}^{Pr}

, as discussed in where we noted the rate of change with mechanical pressure exceeds the change with chemical pressure by a factor of ∼2.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Magnetic transitions and the magnetocaloric effect in the Pr_1−xY_xMn₂Ge₂ system

Wang

Campbell

Din

et al. 2014

Physica Status Solidi (a)

View full text Add to dashboard Cite

show abstract

“…In a perpendicular direction to c-axis, U atoms form planes at z = 0 and 1/2 that are interlayered by Mn 2 Ge 2 groups containing Mn at z = 1/4 and 3/4 on one hand and Ge at z ≈ ±0.375 and ±0.125 on the other hand. High pressure X-ray diffraction measurements [4] show that the compression along c is slightly more (3.7%) compared to compression along a (2.5%). Table 1 shows the pressure dependence of the lattice constants which were utilized in our band structure calculations.…”

Section: Crystal Structurementioning

confidence: 96%

“…Hence, it is appropriate to study this system as a function of external pressure, wherein one could observe the effects of changed inter-atomic distance keeping the 3d electron concentration unaltered. Earlier, high pressure X-ray diffraction studies on UMn 2 Ge 2 have shown that the structure remains stable up to a pressure of 12 GPa and the values of the bulk modulus and its pressure derivative obtained indicate that the degree of itinerancy of 5f states is much less as compared to other uranium compounds [4]. It was also proposed therein that with increasing pressure, hybridization effects would start dominating and lead to decrease of magnetic moments.…”

Section: Introductionmentioning

confidence: 94%