Paramagnetic resonance studies in ferroelectric tris-sarcosine calcium chloride

Windsch, W.

doi:10.1080/00150197608241394

Cited by 49 publications

(13 citation statements)

References 16 publications

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“…As illustrated in Figure b, the obtained critical part of homogeneous line width Γ pp,c = Γ pp – Γ pp,0 follows the logarithmic temperature dependence at T > T c . The same behavior of the EPR line width was observed in manganese-doped TSCC, which exhibits an order–disorder ferroelectric phase transition caused by hydrogen bonding. , Such a logarithmic temperature dependence of the spin–lattice relaxation time is also frequently encountered in nuclear magnetic resonance studies of various H-bonded ferroelectrics. − The logarithmic divergence indicates an order–disorder transition influenced by the anisotropic long-range dipolar forces. Such an uniaxial ordering is often observed for H-bonded ferroelectric or antiferroelectric phases .…”

Section: Results and Discussionmentioning

confidence: 58%

“…Nevertheless, the observed anomaly implies a decrease of T 2 at the phase transition temperature, since broadening of the homogeneous lines of the individual spin packets would also increase the observed inhomogeneous EPR line width. Such an anomalous behavior of Γ pp is caused by a critical slowing down of the order-parameter fluctuations, and it is usually encountered while studying phase transition phenomena in TGS, TSCC, , SrTiO 3 , and other similar systems . An anomaly of T 2 is frequently complemented with a change of T 1 ; , however, as already mentioned, due to too fast relaxation at T c , the direct pulse EPR measurements of relaxation times were not possible in 1 .…”

Section: Results and Discussionmentioning

confidence: 99%

“…The same behavior of the EPR line width was observed in manganese-doped TSCC, which exhibits an order−disorder ferroelectric phase transition caused by hydrogen bonding. 47,54 Such a logarithmic temperature dependence of the spin−lattice relaxation time is also frequently encountered in nuclear magnetic resonance studies of various H-bonded ferroelectrics. 55−57 The logarithmic divergence indicates an order− disorder transition influenced by the anisotropic long-range dipolar forces.…”

Section: ■ Introductionmentioning

confidence: 99%

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EPR of Structural Phase Transition in Manganese- and Copper-Doped Formate Framework of [NH₃(CH₂)₄NH₃][Zn(HCOO)₃]₂

et al. 2016

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Electron paramagnetic resonance (EPR) and pulse electron–nuclear double resonance (ENDOR) spectroscopies are applied to investigate the structural phase transition and the low temperature phase in manganese- and copper-doped [NH3(CH2)4NH3][Zn(HCOO)3]2 dense metal–organic framework. Continuous-wave (CW) EPR measurements indicate successful incorporation of Mn2+ and Cu2+ ions at the Zn2+ lattice sites. Pulse ENDOR spectrum reveals at least four different proton species in the vicinity of the Mn2+ center showing excellent agreement with the X-ray diffraction experiments. Temperature-dependent CW EPR spectra demonstrate that Mn2+ and Cu2+ local paramagnetic probes are sensitive to the phase transition in the studied compounds. The analysis of the temperature dependence of the Cu2+ hyperfine coupling parameter reveals a first-order phase transition at T c = 235 K into an antiferroelectric phase that is close to the tricritical point. The obtained logarithmic divergence of the line width of the Mn2+ EPR spectrum indicates an order–disorder-type phase transition.

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Section: Results and Discussionmentioning

confidence: 58%

Section: Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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EPR of Structural Phase Transition in Manganese- and Copper-Doped Formate Framework of [NH₃(CH₂)₄NH₃][Zn(HCOO)₃]₂

et al. 2016

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“…First, it could be related to the sudden change of the axial zfs parameter at T 0 , which causes the broadening of the hf lines of the central fs transition. On the other hand, such an anomalous behavior is frequently observed in many other ferroelectric and related materials, e.g., triglycine sulfate, trissarcosine calcium chloride, , SrTiO 3 , and others . It is attributed to the critical slowing down of the order parameter fluctuations.…”

Section: Resultsmentioning

confidence: 94%

Spectroscopic Study of [(CH₃)₂NH₂][Zn(HCOO)₃] Hybrid Perovskite Containing Different Nitrogen Isotopes

et al. 2018

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We present a combined differential scanning calorimetry (DSC) and infrared (IR), Raman, electron paramagnetic resonance (EPR), and NMR spectroscopy study of dimethylammonium zinc formate frameworks [(CH 3 ) 2 NH 2 ][Zn(HCOO) 3 ] containing 14 N and 15 N nitrogen isotopes. The DSC reveals very small differences in the phase-transition temperatures for both compounds. The IR and Raman spectroscopies indicate different frequencies of the vibrational modes that involve a nitrogen atom. The temperature-dependent IR and Raman spectra also show a tiny isotope effect on the properties and temperature of the phase transition. The EPR measurements are performed for both compounds doped with small amount of paramagnetic Mn 2+ ions. The obtained continuous-wave Mn 2+ EPR spectra of the disordered phase are very similar for both frameworks, whereas the temperature dependence of the zero-field splitting parameter indicates a slightly different distortion of the MnO 6 octahedra in the low-temperature phase. The EPR line width analysis reveals that the activation energy of the (CH 3 ) 2 NH 2 + cation hopping in the disordered phase is 0.21 eV for both compounds. The 15 N NMR spectroscopy measurements of the framework containing the 15 N isotope are used to directly probe this motion. The obtained temperature dependence of the spin−lattice relaxation time is approximated using the same value of the activation energy as determined from the EPR spectroscopy. The negligible nitrogen isotope effect indicates an order−disorder nature of the phase transitions in the investigated compounds.

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“…This would mean that more conventional classical or quantum critical behaviour would be expected over a wider range of temperatures and tuning parameters. TSCC is hydrogen bonded and was characterized in the past as order‐disorder albeit with no direct supporting evidence . Since the time of these studies TSCC has come to be a prototypical displacive ferroelectrics, as demonstrated by the existence of an under‐damped soft mode.…”

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confidence: 99%

Phase Transitions in the Brominated Ferroelectric Tris‐Sarcosine Calcium Chloride

et al. 2014

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9 ] However, the ultra-weak nature of the dipole moment in TSCC referred to below may reduce the effects of such long-range dipole interactions to a narrow temperature region around the critical point. This would mean that more conventional classical or quantum critical behaviour would be expected over a wider range of temperatures and tuning parameters. TSCC is hydrogen bonded and was characterized in the past as order-disorder albeit with no direct supporting evidence. [ 16,17 ] Since the time of these studies TSCC has come to be a prototypical displacive ferroelectrics, [ 18 ] as demonstrated by the existence of an under-damped soft mode. This mode can be followed into the GHz frequency regime [ 19 ] from high-T values of ca 630 GHz = 21 cm −1 . Deuteration [ 20 ] produces little change in T C , implying that the transition is not controlled by the N-Cl-hydrogen bonds, a result compatible with the soft-mode mechanism operating in TSCC. [ 2 ] The Curie constant of pure TSCC is 27 K, the smallest known Curie constant of any known ferroelectric. By way of comparison, typical values for oxide perovskites such as BaTiO 3 are 50 000 K. This puts TSCC in the family of ultra-weak ferroelectrics. An unrelated form of weak ferroelectricity arises in certain multiferroics where small polarizations are induced by magneto-electric coupling. In pure TSCC, the Curie constants near T C = 130 K, taken as the inverse slopes of the inverse dielectric constants versus temperature above and below T C , differ by a factor of 2.0. This ratio is that predicted by the simplest mean-fi eld Landau theory of phase transitions, but in fact exists in almost no other known ferroelectric. The ratio between the slopes in other ferroelectrics is typically greater than two due to the coupling between lattice strain and polarization. [ 21 ] Under modest pressures pure TSCC becomes what has been termed antiferroelectric, [ 22 ] although no supporting X-ray or dielectric evidence has been given for that label. Four additional enigmatic anomalies have been detected at 42 K, 64 K, 185 K, and another at 283 K [ 3 ] at ambient pressures. The supposed phase transition found near 283 K was described as a modulated quasi-hexagonal phase. [ 23 ] Another possible phase transition was found near 185 K as observed in the relaxation time in proton nuclear magnetic resonance (NMR) spectroscopy. [ 24 ] An additional phase transition was found using specifi c heat at 64 K [ 25 ] and verifi ed by dielectric loss and ultrasonic spectroscopy measurements. [ 26 ] A fourth transition was found near 42 K in dielectric measurements, [ 27 ] and was later confi rmed by resonant ultrasonic spectroscopy (RUS) [ 19 ] and specifi c-heat measurements. At present these anomalies involve unknown changes in the structure.Some studies have reported the phase transition at 64 K (by either dielectric or specifi c-heat data), and some studies have Quantum phase transitions occur in the halide salts of trissarcosine. [ 1 ] Substitution of bromine or iodine for chlorine in (CH 3 NHCH...

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Paramagnetic resonance studies in ferroelectric tris-sarcosine calcium chloride

Cited by 49 publications

References 16 publications

EPR of Structural Phase Transition in Manganese- and Copper-Doped Formate Framework of [NH₃(CH₂)₄NH₃][Zn(HCOO)₃]₂

EPR of Structural Phase Transition in Manganese- and Copper-Doped Formate Framework of [NH₃(CH₂)₄NH₃][Zn(HCOO)₃]₂

Spectroscopic Study of [(CH₃)₂NH₂][Zn(HCOO)₃] Hybrid Perovskite Containing Different Nitrogen Isotopes

Phase Transitions in the Brominated Ferroelectric Tris‐Sarcosine Calcium Chloride

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Paramagnetic resonance studies in ferroelectric tris-sarcosine calcium chloride

Cited by 49 publications

References 16 publications

EPR of Structural Phase Transition in Manganese- and Copper-Doped Formate Framework of [NH3(CH2)4NH3][Zn(HCOO)3]2

EPR of Structural Phase Transition in Manganese- and Copper-Doped Formate Framework of [NH3(CH2)4NH3][Zn(HCOO)3]2

Spectroscopic Study of [(CH3)2NH2][Zn(HCOO)3] Hybrid Perovskite Containing Different Nitrogen Isotopes

Phase Transitions in the Brominated Ferroelectric Tris‐Sarcosine Calcium Chloride

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EPR of Structural Phase Transition in Manganese- and Copper-Doped Formate Framework of [NH₃(CH₂)₄NH₃][Zn(HCOO)₃]₂

EPR of Structural Phase Transition in Manganese- and Copper-Doped Formate Framework of [NH₃(CH₂)₄NH₃][Zn(HCOO)₃]₂

Spectroscopic Study of [(CH₃)₂NH₂][Zn(HCOO)₃] Hybrid Perovskite Containing Different Nitrogen Isotopes