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1

EPR Application in the Study of K_{3}H(SO_{4})_{2} Proton Conductor Doped with Mn^{2+} or VO^{2+} Ions

100%

Waplak S.

Acta Physica Polonica A

|

1994

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vol. 86

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issue 6

939-945

EN

The EPR of Mn^{2+}- or VO^{2+}-doped superprotonic conductor K_{3}H(SO_{4})_{2} is studied in the 80-471 K temperature range. VO^{2+} EPR spectrum reveals diffusion induced merging of proton transferred superhyperfine structure above 380 K. Line width anomaly is observed in Mn^{2+} 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.

2

Investigations of Phase Transitions in (NH_{4})_{3}H(SO_{4})_{2} Crystal by Means of Mn^{2+} EPR Spectra

64%

Bednarski W., Waplak S.

Acta Physica Polonica A

|

1996

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vol. 90

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issue 6

1185-1192

EN

EPR of Mn^{2+} impurity ion in the (NH_{4})_{3}H(SO_{4})_{2} crystal is studied in the temperature range 80-420 K. It is shown that Mn^{2+} substitutes NH_{4}^{+}(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.

3

EPR Study of Monoclinic RbD_{2}PO_{4} Monocrystal Doped with Cr^{5+} Ion

64%

Waplak S., Shuvalov L.

Acta Physica Polonica A

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1995

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vol. 87

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issue 3

643-648

EN

Deuterated monoclinic RbD_{2}PO_{4} (DRDP) doped with chromium Cr^{5+} is studied by EPR in 90 K to 400 K temperature range. EPR reveals two types of paramagnetic centers: single Cr^{5+} (S = 1/2) complex and Cr^{5+}-Cr^{5+} coupled pairs with effective spin S = 1. The EPR line splitting of single Cr^{5+} 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.

4

Electron Paramagnetic Resonance Study of the [(CH_3)_2NH_2]_5Cd_3Cl_{11} Monocrystal Doped with Cu^{2+} ion

51%

Ostrowski A., Bednarski W., Waplak S., Czapla Z.

Acta Physica Polonica A

|

2002

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vol. 101

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issue 6

893-899

EN

The paper reports the electron paramagnetic resonance investigation of Cu^{2+} doped [(CH_3)_2NH_2]_5Cd_3Cl_{11} (DMACC) monocrystal. DMACC:Cu^{2+} was studied in the temperature range (6÷293) K. We did not observe any anomalies of spin-Hamiltonian parameters of Cu^{2+} ion corresponding to the temperature anomalies observed in dielectric studies. The electron paramagnetic resonance anomaly recorded at about 40 K results from the subtle changes in bonds angles and Cu-Cl distances and suggests the smooth second order transition.

5

Microwave X-Band Resonances in Doped Cd₂Nb₂O₇ Monocrystals

51%

Waplak S., Ostrowski A., Wencka M., Bednarski W.

Acta Physica Polonica A

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2017

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vol. 132

|

issue 1

7-11

EN

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.

6

EPR Study of VO^{2+} Center in Fast Proton Conductor K_3H(SO_4)_2

51%

Ostrowski A., Waplak S., Bednarski W.

Acta Physica Polonica A

|

2005

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vol. 108

|

issue 1

127-135

EN

The pretransitional phenomena of superprotonic phase transition (T_{sp}=471 K) were studied in detail by X-band continuous wave EPR spectra of K_3H(SO_4)_2 crystal doped with VO^{2+} ions. Three kinds of VO^{2+} complexes (magnetically equivalent but structurally non-equivalent) denoted as VO^{2+}(I), VO^{2+}(II), and VO^{2+}(III) were found. "Smearing out" of the superhyperfine structure was observed as a result of interbond proton motion. VO^{2+} impurity replaces K^+ ion and experiences the same average crystal field gradient at T_{sp}=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.

7

Pretransition Phenomena in Fast-Proton Conductors

51%

Waplak S., Bednarski W., Ostrowski A.

Acta Physica Polonica A

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2005

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vol. 108

|

issue 2

261-270

EN

In this paper we present recent experimental results related to nonlinear crystal field fluctuations and current flow in K_3H(SO_4)_2 fast-proton conductor far below the transition temperature T_g. The results for crystalline and powdered samples are quantitatively explained in the framework of soliton model of charge transport.

8

EPR Study of Cu^{2+} Doped Fast-Proton Conductor K_3H(SO_4)_2 in the Temperature Range 100-450 K

51%

Ostrowski A., Bednarski W., Waplak S.

Acta Physica Polonica A

|

2003

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vol. 104

|

issue 6

549-558

EN

The K_3H(SO_4)_2 doped with Cu^{2+} ion was studied in detail by X-band CW EPR. Two kinds of Cu^{2+} complexes (magnetically and structurally nonequivalent) denoted as Cu^{2+}(I) and Cu^{2+}(II) were found. Spin-Hamiltonian parameters, direction cosines, and coordination of Cu^{2+} ion were determined at room temperature. The superhyperfine structure was observed below 250 K as a result of interacting of Cu^{2+} ion with four equivalent protons (I=1/2). Temperature studies of K_3H(SO_4)_2 crystal show that interbond motion as a precursor of superprotonic phase transition occurs at above≈250 K.

9

Magnetic Properties in Mn Pure Powder

51%

Szlaferek A., Baszyński J., Waplak S., Jóźwiak K.

Acta Physica Polonica A

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1997

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vol. 92

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issue 2

311-314

EN

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.

10

Magnetic Properties of Epitaxial Fe/(Ga,Mn)As Hybrids

27%

Kalbarczyk K., Dziatkowski K., Szczytko J., Gosk J., Tokarczyk M., Kowalski G., Twardowski A., Bednarski W., Ostrowski A., Waplak S., Martinek J., Liu X., Furdyna J.

Acta Physica Polonica A

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2013

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vol. 124

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issue 5

873-876

EN

Thin-film structures composed of two kinds of ferromagnetic material - metallic Fe and semiconducting (Ga,Mn)As - were investigated by means of SQUID magnetometry and ferromagnetic resonance spectroscopy. Dependence of remnant magnetic moment on temperature showed unexpected anisotropic features when recorded along two orthogonal in-plane directions. For one of these orientations, the change in sign of the slope of m(T) curve at the Curie point of (Ga,Mn)As was observed, while for the other, an analogous m(T) curve retained monotonic character. Based on the comparison with ferromagnetic resonance data, the apparent non-monotonicity was attributed to the temperature-induced change of balance between the external magnetic field and uniaxial magnetic anisotropy in the plane of Fe layer.

Refine search results

EPR Application in the Study of K_{3}H(SO_{4})_{2} Proton Conductor Doped with Mn^{2+} or VO^{2+} Ions

Investigations of Phase Transitions in (NH_{4})_{3}H(SO_{4})_{2} Crystal by Means of Mn^{2+} EPR Spectra

EPR Study of Monoclinic RbD_{2}PO_{4} Monocrystal Doped with Cr^{5+} Ion

Electron Paramagnetic Resonance Study of the [(CH_3)_2NH_2]_5Cd_3Cl_{11} Monocrystal Doped with Cu^{2+} ion

Microwave X-Band Resonances in Doped Cd₂Nb₂O₇ Monocrystals

EPR Study of VO^{2+} Center in Fast Proton Conductor K_3H(SO_4)_2

Pretransition Phenomena in Fast-Proton Conductors

EPR Study of Cu^{2+} Doped Fast-Proton Conductor K_3H(SO_4)_2 in the Temperature Range 100-450 K

Magnetic Properties in Mn Pure Powder

Magnetic Properties of Epitaxial Fe/(Ga,Mn)As Hybrids