skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Pressure–Temperature Phase Diagram Reveals Spin–Lattice Interactions in Co[N(CN) 2 ] 2

Abstract

Diamond anvil cell techniques, synchrotron-based infrared and Raman spectroscopies, and lattice dynamics calculations are combined with prior magnetic property work to reveal the pressure–temperature phase diagram of Co[N(CN)2]2. The second-order structural boundaries converge on key areas of activity involving the spin state exposing how the pressure-induced local lattice distortions trigger the ferromagnetic → antiferromagnetic transition in this quantum material.

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [2];  [3];  [4];  [5]
  1. Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
  2. Division of Materials Research, National Science Foundation, Arlington, Virginia 22230, United States
  3. Department of Chemistry and Biochemistry, Eastern Washington University, Cheney, Washington 99004, United States
  4. Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, Texas 77204, United States
  5. Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, United States
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1409589
Report Number(s):
BNL-114641-2017-JA¿¿¿
Journal ID: ISSN 0020-1669
DOE Contract Number:
SC0012704
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorganic Chemistry; Journal Volume: 56; Journal Issue: 9
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Musfeldt, J. L., O’Neal, K. R., Brinzari, T. V., Chen, P., Schlueter, J. A., Manson, J. L., Litvinchuk, A. P., and Liu, Z. Pressure–Temperature Phase Diagram Reveals Spin–Lattice Interactions in Co[N(CN) 2 ] 2. United States: N. p., 2017. Web. doi:10.1021/acs.inorgchem.6b03097.
Musfeldt, J. L., O’Neal, K. R., Brinzari, T. V., Chen, P., Schlueter, J. A., Manson, J. L., Litvinchuk, A. P., & Liu, Z. Pressure–Temperature Phase Diagram Reveals Spin–Lattice Interactions in Co[N(CN) 2 ] 2. United States. doi:10.1021/acs.inorgchem.6b03097.
Musfeldt, J. L., O’Neal, K. R., Brinzari, T. V., Chen, P., Schlueter, J. A., Manson, J. L., Litvinchuk, A. P., and Liu, Z. Fri . "Pressure–Temperature Phase Diagram Reveals Spin–Lattice Interactions in Co[N(CN) 2 ] 2". United States. doi:10.1021/acs.inorgchem.6b03097.
@article{osti_1409589,
title = {Pressure–Temperature Phase Diagram Reveals Spin–Lattice Interactions in Co[N(CN) 2 ] 2},
author = {Musfeldt, J. L. and O’Neal, K. R. and Brinzari, T. V. and Chen, P. and Schlueter, J. A. and Manson, J. L. and Litvinchuk, A. P. and Liu, Z.},
abstractNote = {Diamond anvil cell techniques, synchrotron-based infrared and Raman spectroscopies, and lattice dynamics calculations are combined with prior magnetic property work to reveal the pressure–temperature phase diagram of Co[N(CN)2]2. The second-order structural boundaries converge on key areas of activity involving the spin state exposing how the pressure-induced local lattice distortions trigger the ferromagnetic → antiferromagnetic transition in this quantum material.},
doi = {10.1021/acs.inorgchem.6b03097},
journal = {Inorganic Chemistry},
number = 9,
volume = 56,
place = {United States},
year = {Fri Apr 07 00:00:00 EDT 2017},
month = {Fri Apr 07 00:00:00 EDT 2017}
}
  • The pressure-temperature phase diagram of the highest-{ital T}{sub {ital c}} organic superconductor, {kappa}-(BEDT-TTF){sub 2}Cu(N(CN){sub 2})Cl is determined, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene. Semiconducting, insulating, metallic, and superconducting regimes are seen at pressures below 1 kbar. Superconductivity at 12.5 K and 0.3 kbar {ital increases} by 0.5--1.5 K upon deuteration of BEDT-TTF, in striking contrast to the normal isotope effect determined previously for {kappa}-(BEDT-TTF){sub 2}Cu(N(CN){sub 2})Br.
  • We present high-resolution measurements of the coefficient of thermal expansion {alpha}(T)={partial_derivative} ln l(T)/{partial_derivative}T of the quasi-two-dimensional (quasi-2D) salts {kappa}-(BEDT-TTF){sub 2}X with X=Cu[N(CN){sub 2}]Cl, Cu[N(CN){sub 2}]Br and Cu(NCS){sub 2} in the temperature range T<{approx}150 K. Three distinct kinds of anomalies corresponding to different temperature ranges have been identified. These are (A) phase-transition anomalies into the superconducting (X=Cu(NCS){sub 2}, Cu[N(CN){sub 2}]Br) and antiferromagnetic (X=Cu[N(CN){sub 2}]Cl) ground state, (B) phase-transition-like anomalies at intermediate temperatures (30-50) K for the superconducting salts, and (C) kinetic, glasslike transitions at higher temperatures, i.e., (70-80) K for all compounds. By a thermodynamic analysis of the discontinuities at themore » second-order phase transitions that characterize the ground state of system (A), the uniaxial-pressure coefficients of the respective transition temperatures could be determined. We find that in contrast to what has been frequently assumed, the intraplane-pressure coefficients of Tc for this family of quasi-2D superconductors do not reveal a simple form of systematics. This demonstrates that attempts to model these systems by solely considering in-plane electronic parameters are not appropriate. At intermediate temperatures (B), distinct anomalies reminiscent of second-order phase transitions have been found at T*=38 K and 45 K for the superconducting X=Cu(NCS){sub 2} and Cu[N(CN){sub 2}]Br salts, respectively. Most interestingly, we find that the signs of the uniaxial pressure coefficients of T*, {partial_derivative}T*/{partial_derivative}p{sub i} (i=a,b,c), are strictly anticorrelated with those of {Tc}. Based on comparative studies including the nonsuperconducting X=Cu[N(CN){sub 2}]Cl salt as well as isotopically labeled compounds, we propose that T* marks the transition to a density-wave state forming on minor, quasi-1D parts of the Fermi surface. Our results are compatible with two competing order parameters that form on disjunct portions of the Fermi surface. At elevated temperatures (C), all compounds show {alpha}(T) anomalies that can be identified with a kinetic, glasslike transition where, below a characteristic temperature T{sub g}, disorder in the orientational degrees of freedom of the terminal ethylene groups becomes frozen in. Our results provide a natural explanation for the unusual time- and cooling-rate dependences of the ground-state properties in the hydrogenated and deuterated Cu[N(CN){sub 2}]Br salts reported in the literature.« less
  • The spin-liquid candidate {kappa}-(BEDT-TTF){sub 2}Cu{sub 2}(CN){sub 3} has been studied by measuring the uniaxial expansion coefficients {alpha}{sub i}, the specific heat, and magnetic susceptibility. Special emphasis was placed on the mysterious anomaly around 6K - a potential spin-liquid instability. Distinct and strongly anisotropic lattice effects have been observed at 6K, clearly identifying this feature as a second-order phase transition. Owing to the large anomalies in {alpha}{sub i}, the application of Grueneisen scaling has enabled us to determine the corresponding specific heat contribution and the entropy release. Comparison of the latter with available spin models suggests that spin degrees of freedommore » alone cannot account for the phase transition. Scenarios, involving charge degrees of freedom, are discussed.« less
  • The heterometallic complex (NH{sub 3}){sub 2}YbFe(CO){sub 4} was prepared from the reduction of Fe{sub 3}(CO){sub 12} by Yb in liquid ammonia. Ammonia was displaced from (NH{sub 3}){sub 2}YbFe(CO){sub 4} by acetonitrile in acetonitrile solution, and the crystalline compounds ([(CH{sub 3}CN){sub 3}YbFe(CO){sub 4}]{sub 2}{center_dot}CH{sub 3}CN){sub infinity} showed that it is a ladder polymer with direct Yb-Fe bonds. In the present study, an X-ray crystal structure analysis also showed that [(CH{sub 3}CN){sub 3}YbFe(CO){sub 4}]{sub infinity} showed that it is a ladder polymer with direct Yb-Fe bonds. In the present study, an X-ray crystal structure analysis also showed that [(CH{sub 3}CN){sub 3}YbFe(CO){sub 4}]{submore » infinity} is a sheetlike array with direct Yb-Fe bonds. Electrical conductivity measurements in acetonitrile show that these acetonitrile complexes are partially dissociated into ionic species. IR and NMR spectra of the solutions reveal the presence of [HFe(CO){sub 4}]{sup {minus}}. However, upon recrystallization, the acetonitrile complexes show no evidence for the presence of [HFe(CO){sub 4}]{sup {minus}}. However, upon recrystallization, the acetonitrile complexes show no evidence for the presence of [HFe(CO){sub 4}]{sup {minus}} on the basis of their IR spectra. The solid state MAS {sup 2}H NMR spectra of deuterated acetonitrile complexes give no evidence for [{sup 2}HFe(CO){sub 4}]{sup {minus}}. It appears that the rupture of the Yb-Fe bond could occur in solution to generate the ion pair [L{sub n}Yb]{sup 2+}[Fe(CO){sub 4}]{sup 2{minus}}, but then the highly basic [Fe(CO){sub 4}]{sup 2{minus}} anion could abstract a proton from a coordinated acetonitrile ligand to form [HF3(CO){sub 4}]{sup {minus}}. However, upon crystallization, the proton could be transferred back to the ligand, which results in the neutral polymeric species.« less
  • Addition of (NO)(BF{sub 4}) to CH{sub 3}CNW(CO){sub 5} in CH{sub 2}Cl{sub 2} gives a mixture of five mononitrosyl compounds, mer-(cis-CH{sub 3}CN)(trans-NO)(CO){sub 3}W({mu}-F)BF{sub 3} (1), (mer,cis-(CH{sub 3}CN){sub 2}W(CO){sub 3}(NO))(BF{sub 4}) (2a), cis,cis,trans-(CH{sub 3}CN){sub 2}(CO){sub 2}(NO)W({mu}-F)BF{sub 3} (3), (fac-(CH{sub 3}CN){sub 3} W(CO){sub 2}(NO))(BF){sub 4} (4a), and trans-(NO)(CO){sub 4}W({mu}-F)BF{sub 3} (5); in a typical experiment the yield is 90%, and the ratio 1:2a:3:4a:5 is 47:14:11:1:27. Support for the identities of 1-5 is obtained by reaction of the mixture with Me{sub 3}P, giving (mer-(cis-CH{sub 3}CN)(trans-Me{sub 3}P)W(CO){sub 3}(NO))(BF{sub 4}) (7a), (cis,cis,trans-(CH{sub 3}CN){sub 2}(CO){sub 2}(NO)W(PMe{sub 3}))(BF{sub 4}) (8a), (trans-Me{sub 3}P(CO){sub 4}WNO)(BF{sub 4}) (9), and the previouslymore » reported compound (mer,cis-(Me{sub 3}P){sub 2}W(CO){sub 3}(NO))(BF{sub 4}) (10a). The reaction mixtures are analyzed by IR and {sup 1}H, {sup 13}C, and {sup 19}F NMR spectroscopy. In particular, the {sup 13}C NMR spectrum exhibits quintets for the carbonyl ligands of 1,3, 5 due to a dynamic spinning process of the (({mu}-F)BF{sub 3}){sup {minus}} ligand, and the {sup 19}F NMR spectrum exhibits doublets for the terminal fluorine atoms (which are further separated into {sup 10}B and {sup 11}B isotopomers) near {minus}153 ppM and quartets for the bridging fluorine atoms from {minus}203 to {minus}238 ppM. Independent synthesis and isolation in good yield of 2b-c, 4a-d, 7b-c, and 8b (where the anions for a-d are (BF{sub 4}){sup {minus}}, (SbF{sub 6}){sup {minus}}, ((C{sub 6}H{sub 5}){sub 4}B){sup {minus}}, and (PF{sub 6}){sup {minus}}{sup {minus}}, respectively) are described, as are the independent synthesis and spectroscopic characterization of 3, 5, and 6. 4 figs., 1 tab.« less