32 research outputs found
EPR Application in the Study of KH(SO) Proton Conductor Doped with Mn or VO Ions
The EPR of Mn- or VO-doped superprotonic conductor KH(SO) is studied in the 80-471 K temperature range. VO EPR spectrum reveals diffusion induced merging of proton transferred superhyperfine structure above 380 K. Line width anomaly is observed in Mn EPR spectrum which is attributed to the intrabond and interbond proton motions, these lead to high protonic conductivity. It is shown that paramagnetic centers namely of electronic spin greater than 1, with excess charge compensated by the protonic vacancy, are good probes to monitor the protonic conductivity on molecular level
Pretransition Phenomena in Fast-Proton Conductors
In this paper we present recent experimental results related to nonlinear crystal field fluctuations and current flow in KH(SO) fast-proton conductor far below the transition temperature T. The results for crystalline and powdered samples are quantitatively explained in the framework of soliton model of charge transport
EPR Study of Cu Doped Fast-Proton Conductor KH(SO) in the Temperature Range 100-450 K
The KH(SO) doped with Cu ion was studied in detail by X-band CW EPR. Two kinds of Cu complexes (magnetically and structurally nonequivalent) denoted as Cu(I) and Cu(II) were found. Spin-Hamiltonian parameters, direction cosines, and coordination of Cu ion were determined at room temperature. The superhyperfine structure was observed below 250 K as a result of interacting of Cu ion with four equivalent protons (I=1/2). Temperature studies of KH(SO) crystal show that interbond motion as a precursor of superprotonic phase transition occurs at above≈250 K
INFLUENCE OF SPONTANEOUS POLARIZATION ON THE EPR SPECTRA OF Cr3+ IONS IN TGFB
Le spectre EPR de l'ion Cr3+ du TGFB est étudié en fonction de la température au voisinage du point de Curie. Au-dessus du point de Curie, le champ cristallin agissant sur l'ion Cr3+ montre que la symétrie est cubique tandis qu'au-dessous du point de Curie la polarisation spontanée perturbe le champ cristallin cubique et la symétrie devient rhombique.The EPR spectrum of Cr3+ ion in TGFB was examined versus temperature near the Curie point. Above the Curie point the crystal field acting on Cr3+ ion indicate the Cubic symmetry whereas below the Curie point the spontaneous polarization disturbs the Cubic crystal field and the symmetry becomes rhombic
Investigations of Phase Transitions in (NH)H(SO) Crystal by Means of Mn EPR Spectra
EPR of Mn impurity ion in the (NH)H(SO) crystal is studied in the temperature range 80-420 K. It is shown that Mn substitutes NH(I) ion and is coordinated in deformed oxygen octahedron in which takes two "off-center" positions. Its spin-Hamiltonian parameters and direction cosines of crystal field are determined. The successive EPR line splitting for three phase transitions is discussed
EPR Study of Monoclinic RbDPO Monocrystal Doped with Cr Ion
Deuterated monoclinic RbDPO (DRDP) doped with chromium Cr is studied by EPR in 90 K to 400 K temperature range. EPR reveals two types of paramagnetic centers: single Cr (S = 1/2) complex and Cr-Cr coupled pairs with effective spin S = 1. The EPR line splitting of single Cr complex in DRDP versus temperature agrees with the unit cell multiplication. The splitting of EPR line of pair spectrum appears at T* = 160 K, far below the phase transition temperatures and is due to the anisotropy of the exchange interaction. The clustering effect in the low-dimensional DRDP is suggested
EPR Study of Cu 2+
The KH(SO) doped with Cu ion was studied in detail by X-band CW EPR. Two kinds of Cu complexes (magnetically and structurally nonequivalent) denoted as Cu(I) and Cu(II) were found. Spin-Hamiltonian parameters, direction cosines, and coordination of Cu ion were determined at room temperature. The superhyperfine structure was observed below 250 K as a result of interacting of Cu ion with four equivalent protons (I=1/2). Temperature studies of KH(SO) crystal show that interbond motion as a precursor of superprotonic phase transition occurs at above≈250 K
EPR Study of VO Center in Fast Proton Conductor KH(SO)
The pretransitional phenomena of superprotonic phase transition (T=471 K) were studied in detail by X-band continuous wave EPR spectra of KH(SO) crystal doped with VO ions. Three kinds of VO complexes (magnetically equivalent but structurally non-equivalent) denoted as VO(I), VO(II), and VO(III) were found. "Smearing out" of the superhyperfine structure was observed as a result of interbond proton motion. VO impurity replaces K ion and experiences the same average crystal field gradient at T=471 K for I- and II-type complexes. The increase in interbond proton frequency hopping above 360 K is a reason of significant line broadening
Magnetic Properties in Mn Pure Powder
The structural and magnetic properties of deformed powder of Mn obtained by mechanical grinding have been investigated using X-ray diffraction and magnetic measurements. The small values of ferromagnetic moment of Mn after grinding are attributed to the formation of a deformed phase at the surface of grains with enlargement of the interatomic spacings at the grains boundaries
Microwave X-Band Resonances in Doped Cd₂Nb₂O₇ Monocrystals
Cadmium pyroniobiate (CNO) is the ferroic material with unusual diffuse phase diagram which includes both relaxor and nanocluster domains. We present the data for CNO crystals with several admixtures of paramagnetic ions studied on X and S microwave bands at zero-external magnetic field and classical EPR conditions. Our results lead to an assertion of a ferroelectric resonance effect due to "electronic ferroelectricity". The data fit well to the Falicov-Kimball theoretical model applicable to strongly-correlated-electron or mixed-valence systems