Critical slowing of quantum atomic deuterium/hydrogen with features of multiferroicity in the geometrically frustrated system Co2(OD)3Cl/C

Hydrogen/Deuterium Dynamics in Hydroxyl Salts Co2(OH)3Br/Co2(OD)3Br Revealed by Muon Spin Relaxation

“…These behaviors are much different to those reported for Co 2 (OD) 3 Cl and Co 2 (OH) 3 Cl, wherein the dielectric constant in Co 2 (OD) 3 Cl showed a sharp peak at T ε = 230 K while in Co 2 (OH) 3 Cl there appeared two individual anomalies near T*~210 K and T**~160 K, respectively. As reported in Reference [12], ferroelectric transition was verified in Co 2 (OD) 3 Cl. Instead, an incomplete ordering process was suggested for Co 2 (OH) 3 Cl.…”

“…In addition, magnetic coupling was also found to be existing below around ~250 K in both Co 2 (OH) 3 Cl and Co 2 (OD) 3 Cl [12]. The present research on Co 2 (OH) 3 Cl/Co 2 (OD) 3 Cl supposes that the ferroelectricity is frustrated [12,13].…”

“…As a matter of fact, an ideal model would have to include the effect of the Co nuclear magnetic fields in the first term in Equation (1), since the [OH]−/[OD]− -site muons would also sense the dipolar fields of Co nuclei. However, this kind of function, described in Reference [12], is experimentally unavailable at the present time and technically it is unpractical to perform the fitting using a combination of a KT function multiplied by the DKT function. Consequently Equation (1) is the most appropriate and practical one for the present study.…”

“…Since neither magnetic order nor obvious structure transition exists in this temperature range, the ferroelectricity in the present materials are not caused by a certain type of magnetic ordering such as the magnetic ordering inducing ferroelectricity reported in TbMnO 3 [10] and R CrO 3 [11], due to the magnetic transition occurring at T N = 10.5 K in Co 2 (OD) 3 Cl ( T N1 = 6.2 K and T N2 = 4.8 K in Co 2 (OD) 3 Br) [9], which is much lower than the ferroelectric transition temperatures. By combining data from muon spin relaxation ( μ SR) and Raman spectroscopy experiments, we provided clear evidence for the ferroelectric transition mechanism in Co 2 (OD) 3 Cl, wherein a critical slowing of quantum D atoms occurred, suggesting deuterium ordering with a subtle structural transition [12]. In addition, magnetic coupling was also found to be existing below around ~250 K in both Co 2 (OH) 3 Cl and Co 2 (OD) 3 Cl [12].…”

“…By combining data from muon spin relaxation ( μ SR) and Raman spectroscopy experiments, we provided clear evidence for the ferroelectric transition mechanism in Co 2 (OD) 3 Cl, wherein a critical slowing of quantum D atoms occurred, suggesting deuterium ordering with a subtle structural transition [12]. In addition, magnetic coupling was also found to be existing below around ~250 K in both Co 2 (OH) 3 Cl and Co 2 (OD) 3 Cl [12]. The present research on Co 2 (OH) 3 Cl/Co 2 (OD) 3 Cl supposes that the ferroelectricity is frustrated [12,13].…”