Glassy Dynamics Under Superhigh Pressure (2009)
Pronin, A. A., Kondrin, M. V., Lyapin, A. G., Brazhkin, V. V., Volkov, A. A., Lunkenheimer, P., ...
Nearly all glass-forming liquids feature, along with the structural alpha-relaxation process, a faster secondary process (beta-relaxation), whose nature belongs to the great mysteries of glass...
On the room temperature multiferroic BiFeO3: Magnetic, dielectric and thermal properties (2009)
Lu, Jun, Günther, A., Schrettle, F., Mayr, F., Krohns, S., Lunkenheimer, P., ...
Magnetic dc susceptibility between 1.5 and 800 K, ac susceptibility and magnetization, thermodynamic properties, temperature dependence of radio and audio-wave dielectric constants and conductivity,...
Krohns, S., Lu, J., Lunkenheimer, P., Brize, V., Autret-Lambert, C., Gervais, M., ...
The present work reports synthesis, as well as a detailed and careful characterization of structural, magnetic, and dielectric properties of differently tempered undoped and doped CaCu3Ti4O12 (CCTO)...
Magnetic susceptibility, phonons and dielectric constant of single crystalline BiFeO3 (2009)
Lu, Jun, Schmidt, M, Lunkenheimer, P, Pimenov, A, Mukhin, A A, Travkin, V D, ...
The magnetic susceptibility between 1.5 and 800 K, the infrared reflectivity at room temperature and the temperature dependence of the dielectric constant at mm-wavelengths are reported for single...
Dielectric constant of Pr2/3Cu3Ti4O12: Colossal as in CaCu3Ti4O12 (2009)
Sebald, J., Krohns, S., Lunkenheimer, P., Ebbinghaus, S. G., Riegg, S., Reller, A., ...
In the present work we demonstrate that in the series Ln2/3Cu3Ti4O12 with Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Tm, the compounds Pr2/3Cu3Ti4O12 and La2/3Cu3Ti4O12 stand out by showing...
Colossal dielectric constant up to GHz at room temperature (2008)
Krohns, S., Lunkenheimer, P., Kant, Ch., Pronin, A. V., Brom, H. B., Nugroho, A. A., ...
The search for new materials with extremely high ("colossal") dielectric constants, required for future electronics, is one of the most active fields of modern materials science. However, the...
Köhler, M., Lunkenheimer, P., Goncharov, Y., Wehn, R., Loidl, A.
We present a thorough characterization of the glassy dynamics of three propylene glycols (mono-, di- and trimer) by broadband dielectric spectroscopy. By covering a frequency range of more than 15...
Colossal magnetocapacitive effect in differently synthesized and doped CdCr2S4 (2008)
Krohns, S., Schrettle, F., Lunkenheimer, P., Tsurkan, V., Loidl, A.
In the present work, we address the question of an impurity-related origin of the colossal magnetocapacitive effect in the spinel system CdCr2S4. We demonstrate that a strong variation in the...
Optical Spectroscopy in CoO: Phonons, Electric, and Magnetic Excitations (2008)
Kant, Ch., Rudolf, T., Schrettle, F., Mayr, F., Deisenhofer, J., Lunkenheimer, P., ...
The reflectivity of single-crystalline CoO has been studied by optical spectroscopy for wave numbers ranging from 100 to 28,000\wn and for temperatures 8 $< T
Relaxations as key to the magnetocapacitive effects in the perovskite manganites (2008)
Schrettle, F., Lunkenheimer, P., Hemberger, J., Ivanov, V. Yu., Mukhin, A. A., Balbashov, A. M., ...
We present a detailed dielectric study of the relaxation effects that occur in several perovskite rare-earth manganites, including the multiferroics TbMnO3 and DyMnO3. We demonstrate that the strong...
Dielectric and conductivity relaxation in mixtures of glycerol with LiCl (2008)
Köhler, M., Lunkenheimer, P., Loidl, A.
We report a thorough dielectric characterization of the alpha relaxation of glass forming glycerol with varying additions of LiCl. Nine salt concentrations from 0.1 - 20 mol% are investigated in a...
Residual dipolar couplings as a tool to study molecular recognition of ubiquitin. (2008)
Lakomek, N. A., Lange, O., Walter, K., Fares, C., Egger, D., Lunkenheimer, P., ...
Schrettle, F., Krohns, S., Lunkenheimer, P., Hemberger, J., Büttgen, N., ...
We present a detailed study of complex dielectric constant and ferroelectric polarization in multiferroic LiCuVO4 as function of temperature and external magnetic field. In zero external magnetic...
Lunkenheimer, P., Pardo, L. C., Köhler, M., Loidl, A.
We have performed a detailed dielectric investigation of the relaxational dynamics of glass-forming benzophenone. Our measurements cover a broad frequency range of 0.1 Hz to 120 GHz and temperatures...
Krohns, S., Lunkenheimer, P., Ebbinghaus, S. G., Loidl, A.
In the present work the authors report results of broadband dielectric spectroscopy on various samples of CaCu3Ti4O12, including so far only rarely investigated single crystalline material. The...
Broadband dielectric response of CaCu3Ti4O12: From dc to the electronic transition regime (2007)
Kant, Ch., Rudolf, T., Mayr, F., Krohns, S., Lunkenheimer, P., Ebbinghaus, S. G., ...
We report on phonon properties and electronic transitions in CaCu3Ti4O12, a material which reveals a colossal dielectric constant at room temperature without any ferroelectric transition. The results...
Pardo, L. C., Lunkenheimer, P., Loidl, A.
We report a thorough characterization of the glassy dynamics of benzophenone by broadband dielectric spectroscopy. We detect a well pronounced beta relaxation peak developing into an excess wing with...
Lunkenheimer, P., Hemberger, J., Tsurkan, V., Staresinic, D., Biljakovic, K., Loidl, A.
In the present work we reply to the Comment by Catalan and Scott (cond-mat/0607500) on two of our papers. This Comment has been rejected from publication in Physical Review Letters and, hence, our...
Broadband dielectric spectroscopy on single-crystalline and ceramic CaCu3Ti4O12 (2006)
Krohns, S., Lunkenheimer, P., Ebbinghaus, S. G., Loidl, A.
We present dielectric measurements of the colossal dielectric constant material CaCu3Ti4O12 extending up to 1.3 GHz also covering so far only rarely investigated single crystalline samples. Special...
Broadband dielectric spectroscopy and aging of glass formers (2006)
Wehn, R., Lunkenheimer, P., Loidl, A.
We present the results of aging experiments on a variety of glass formers, including xylitol, glycerol, propylene carbonate, and [Ca(NO3)2]0.4[KNO3]0.6 (CKN). In addition, broadband dielectric...
Multiferroicity and colossal magneto-capacitance in Cr-thiospinels (2006)
Hemberger, J., Lunkenheimer, P., Fichtl, R., Weber, S., Tsurkan, V., Loidl, A.
The sulfur based Cr-spinels RCr2S4 with R = Cd and Hg exhibit the coexistence of ferromagnetic and ferroelectric properties together with a pronounced magnetocapacitive coupling. While in CdCr2S4...
Lunkenheimer, P., Götzfried, T., Fichtl, R., Weber, S., Rudolf, T., Loidl, A., ...
We present a thorough dielectric investigation of the hexagonal perovskites La1.2Sr2.7IrO7.33 and La1.2Sr2.7RuO7.33 in a broad frequency and temperature range, supplemented by additional infrared...
Tsurkan, V., Hemberger, J., Krimmel, A., Lunkenheimer, P., Weber, S., ...
A detailed study of poly- and single crystalline samples of the normal spinel HgCr2S4 is reported. The structural refinement reveals enhanced values of the atomic displacements suggesting closeness...
The multiferroic phases of (Eu:Y)MnO3 (2006)
Hemberger, J., Schrettle, F., Pimenov, A., Lunkenheimer, P., Ivanov, V. Yu., Mukhin, A. A., ...
We report on structural, magnetic, dielectric, and thermodynamic properties of (Eu:Y)MnO3 for Y doping levels 0
Spin dynamics in the low-dimensional magnet TiOCl (2006)
Zakharov, D. V., Deisenhofer, J., Lunkenheimer, P., Hemberger, J., Hoinkis, M., ...
We present detailed ESR investigations on single crystals of the low-dimensional quantum magnet TiOCl. The anisotropy of the g-factor indicates a stable orbital configuration below room temperature,...
Colossal magnetocapacitance and colossal magnetoresistance in HgCr2S4 (2006)
Weber, S., Lunkenheimer, P., Fichtl, R., Hemberger, J., Tsurkan, V., Loidl, A.
We present a detailed study of the dielectric and charge transport properties of the antiferromagnetic cubic spinel HgCr2S4. Similar to the findings in ferromagnetic CdCr2S4, the dielectric constant...
$\alpha$- and $\beta$- Relaxation Dynamics of a fragile plastic crystal (2006)
Pardo, L. C., Lunkenheimer, P., Loidl, A.
We present a thorough dielectric investigation of the relaxation dynamics of plastic crystalline Freon112, which exhibits freezing of the orientational degrees of freedom into a glassy crystal below...
Rösner, P., Hachenberg, J., Samwer, K., Wehn, R., Lunkenheimer, P., Loidl, A., ...
Abstract. Dynamic loss spectra for laser-deposited poly(methyl methacrylate) (PMMA) films are investigated at a frequency of 5.4 kHz with dielectric spectroscopy and mechanical torsional spectroscopy...
Dielectric spectroscopy on aging glasses (2005)
Lunkenheimer, P., Wehn, R., Loidl, A.
In the present work, we provide further evidence for the applicability of a modified stretched-exponential behavior, proposed recently for the description of aging-time dependent data below the glass...
Dynamic conductivity of semiconducting manganites approaching the metal-insulator transition (2005)
Lunkenheimer, P., Mayr, F., Loidl, A.
We report the frequency-dependent conductivity of the manganite system La1-xSrxMnO3 (x
Staresinic, D., Biljakovic, K., Lunkenheimer, P., Loidl, A.
We present measurements of the dielectric response of quasi one-dimensional (TMTTF)2AsF6 in a wide temperature and frequency range. We provide a thorough characterization of the relaxational dynamics...
Multiferroic behavior in CdCr2X4 (X = S, Se) (2005)
Hemberger, J., Lunkenheimer, P., Fichtl, R., Weber, S., Tsurkan, V., Loidl, A.
The recently discovered multiferroic material CdCr2S4 shows a coexistence of ferromagnetism and relaxor ferroelectricity together with a colossal magnetocapacitive effect. The complex dielectric...
Relaxation dynamics and colossal magnetocapacitive effect in CdCr2S4 (2005)
Lunkenheimer, P., Fichtl, R., Hemberger, J., Tsurkan, V., Loidl, A.
A thorough investigation of the relaxational dynamics in the recently discovered multiferroic CdCr2S4 showing a colossal magnetocapacitive effect has been performed. Broadband dielectric measurements...
Staresinic, D., Lunkenheimer, P., Hemberger, J., Biljakovic, K., Loidl, A.
We report on broadband dielectric spectroscopy on the one-dimensional semiconductor (NbSe4)3I. Below the structural phase transition close to 270 K we observe colossal dielectric constants with a...
Glassy freezing of orbital dynamics in FeCr2S4 and FeSc2S4 (2005)
Fichtl, R., Lunkenheimer, P., Hemberger, J., Tsurkan, V., Loidl, A.
We report on a thorough dielectric investigation of the glass-like freezing of the orbital reorientation-dynamics, recently found for the crystalline sulpho-spinels FeCr2S4 and FeSc2S4. As the...
Lunkenheimer, P., Wehn, R., Schneider, U., Loidl, A.
We present time-dependent dielectric loss data at different frequencies for a variety of glass formers after cooling below the glass temperature. The observed aging dynamics is described using a...
Relaxor ferroelectricity and colossal magnetocapacitive coupling in ferromagnetic CdCr2S4 (2005)
Hemberger, J., Lunkenheimer, P., Fichtl, R., Tsurkan, V., Loidl, A.
Multiferroic materials, which reveal magnetic and electric order, are in the focus of recent solid state research. Especially the simultaneous occurrence of ferroelectricity and ferromagnetism,...
Orbital Freezing in FeCr2S4 Studied by Dielectric Spectroscopy (2004)
Fichtl, R., Lunkenheimer, P., Hemberger, J., Tsurkan, V., Loidl, A.
Broadband dielectric spectroscopy has been performed on single-crystalline FeCr2S4 revealing a transition into a low-temperature orbital glass phase and on polycrystalline FeCr2S4 where long-range...
Non-intrinsic origin of the Colossal Dielectric Constants in CaCu3Ti4O12 (2004)
Lunkenheimer, P., Fichtl, R., Ebbinghaus, S. G., Loidl, A.
The dielectric properties of CaCu3Ti4O12, a material showing colossal values of the dielectric constant, were investigated in a broad temperature and frequency range extending up to 1.3 GHz. A...
Dielectric behavior of Copper Tantalum Oxide (2003)
Renner, B., Lunkenheimer, P., Schetter, M., Loidl, A., Reller, A., Ebbinghaus, S. G.
A thorough investigation of the dielectric properties of Cu2Ta4O12, a material crystallizing in a pseudo-cubic, perovskite-derived structure is presented. We measured the dielectric constant and...
Dielectric properties and dynamical conductivity of LaTiO3: From dc to optical frequencies (2003)
Lunkenheimer, P., Rudolf, T., Hemberger, J., Pimenov, A., Tachos, S., Lichtenberg, F., ...
We provide a complete and detailed characterization of the temperature-dependent response to ac electrical fields of LaTiO3, a Mott-Hubbard insulator close to the metal-insulator transition. We...
The response of disordered matter to electromagnetic fields (2003)
We have studied a variety of different disordered materials, including molecular and ionic liquids, supercooled liquids and glasses, ionic conductors, and doped semiconductors, in ac electromagnetic...
Evidence for Jahn-Teller distortions at the antiferromagnetic transition in LaTiO$_3$ (2003)
Hemberger, J., Fritsch, V., Deisenhofer, J., Lobina, S., Rudolf, T., ...
LaTiO$_3$ is known as Mott-insulator which orders antiferromagnetically at $T_{\rm N}=146$ K. We report on results of thermal expansion and temperature dependent x-ray diffraction together with...
Electrically conducting niobates and titanates of the A§nB§nO§3§n§+§2 type. (2003)
Lichtenberg, F., Kuntscher, C.A., Schuppler, S., Bohnen, K.P., Winter, H., Bobnar, V., ...
10th Internat.Workshop on Oxide Electronics (WOE 10), Augsburg, September 11-13, 2003
'Boson peak' and high-frequency excitations in glassy crystals (2002)
The high-frequency excitations in glasses and supercooled liquids belong to the great mysteries of the physics of condensed matter. While the fast process, located at GHz-THz, can be interpreted as...
Electronic and optical properties of LiBC (2002)
Pronin, A. V., Pucher, K., Lunkenheimer, P., Krimmel, A., Loidl, A.
LiBC, a semiconducting ternary borocarbide constituted of the lightest elements only, has been synthesized and characterized by x-ray powder diffraction, dielectric spectroscopy, and conductivity...
Materials with Colossal Dielectric Constant: Do They Exist? (2002)
Lunkenheimer, P., Bobnar, V., Pronin, A. V., Ritus, A. I., Volkov, A. A., Loidl, A.
Experimental evidence is provided that colossal dielectric constants, epsilon >= 1000, sometimes reported to exist in a broad temperature range, can often be explained by Maxwell-Wagner type...
Dielectric properties of the low dimensional vanadium oxides Ba2V3O9 and Sr2V3O9 (2002)
Bobnar,V., Lunkenheimer,P., Loidl,A., Kaul,E. E., Geibel,C.
The dielectric response of the low-dimensional vanadium oxides Ba2V3O9 and Sr2V3O9 has been investigated in the frequency range of 20 Hz-1 MHz. At low frequencies the dielectric response is governed...
Dielectric properties of the low dimensional vanadium oxides Ba2V3O9 and Sr2V3O9 (2002)
Bobnar, V., Lunkenheimer, P., Loidl, A., Kaul, E. E., Geibel, C.
The dielectric response of the low-dimensional vanadium oxides Ba2V3O9 and Sr2V3O9 has been investigated in the frequency range of 20 Hz-1 MHz. At low frequencies the dielectric response is governed...
Ritus, A. I., Pronin, A. V., Volkov, A. A., Lunkenheimer, P., Loidl, A., Shcheulin, A. S., ...
Physical properties of semiconducting CdF_2 crystals doped with In are determined from measurements of the radio-frequency response of a sample with Schottky barriers at frequencies 10 - 10^6 Hz. The...
Calcium Rubidium Nitrate: Mode-Coupling $\beta$ Scaling without Factorization (2001)
Goldammer, M., Losert, C., Wuttke, J., Petry, W., Terki, F., Schober, H., ...
The fast dynamics of viscous calcium rubidium nitrate is investigated by depolarized light scattering, neutron scattering and dielectric loss. Fast $\beta$ relaxation evolves as in calcium potassium...
Magnetic, electronic, dielectric and optical properties of Pr(Ca:Sr)MnO3 (2001)
Sichelschmidt,J., Paraskevopoulos,M., Brando,M., Wehn,R., Ivannikov,D., Mayr,F., ...
Magnetic, electronic, dielectric and optical properties of Pr(Ca:Sr)MnO3 (2001)
Sichelschmidt, J., Paraskevopoulos, M., Brando, M., Wehn, R., Ivannikov, D., Mayr, F., ...
The excess wing in the dielectric loss of glass-forming ethanol: A relaxation process (2000)
Brand, R., Lunkenheimer, P., Schneider, U., Loidl, A.
A detailed dielectric investigation of liquid, supercooled liquid, and glassy ethanol reveals a third relaxation process, in addition to the two processes already known. The relaxation time of the...
The Excess Wing in the Dielectric Loss of Glass-Formers: A Johari-Goldstein beta-Relaxation? (2000)
Schneider, U., Brand, R., Lunkenheimer, P., Loidl, A.
Dielectric loss spectra of glass-forming propylene carbonate and glycerol at temperatures above and below T_g are presented. By performing aging experiments lasting up to five weeks, equilibrium...
Propylene Carbonate Reexamined: Mode-Coupling $\beta$ Scaling without Factorisation ? (1999)
Wuttke, J., Ohl, M., Goldammer, M., Roth, S., Schneider, U., Lunkenheimer, P., ...
The dynamic susceptibility of propylene carbonate in the moderately viscous regime above $T_{\rm c}$ is reinvestigated by incoherent neutron and depolarised light scattering, and compared to...
Wide range dielectric spectroscopy on glass-forming materials: an experimental overview (1999)
Schneider, U., Lunkenheimer, P., Pimenov, A., Brand, R., Loidl, A.
Dielectric spectroscopy is one of the most commonly used techniques for the investigation of the dynamic response of glass-forming materials. The tremendous slow-down of the particle motions when...
Linear and non-linear dielectric spectroscopy on ammonium doped Rochelle salt (1999)
Schneider, U., Lunkenheimer, P., Hemberger, J., Loidl, A.
In this work we present a thorough investigation of the mixed system of Rochelle salt doped with ammonium, with 0
Fast Dynamics of Glass-forming Liquids investigated by Dielectric Spectroscopy: a Comparison (1999)
Schneider, U., Lunkenheimer, P., Brand, R., Loidl, A.
We have performed dielectric spectroscopy on the molecular glass-formers glycerol, propylene carbonate (PC) and the ionic melts CKN and CRN. The frequency range covers almost 20 decades from some...
Scaling of broadband dielectric data of glass-forming liquids and plastic crystals (1999)
Schneider, U., Brand, R., Lunkenheimer, P., Loidl, A.
The Nagel-scaling and the modified scaling procedure proposed recently by Dendzik et al. have been applied to broadband dielectric data on two glass- forming liquids (glycerol and propylene...
Broadband dielectric response of glycerol and propylene carbonate: a comparison (1998)
Lunkenheimer, P., Schneider, U., Brand, R., Loidl, A.
Dielectric data on glycerol and propylene carbonate covering 18 decades of frequency are presented and compared to each other. Both materials exhibit qualitatively similar behavior except for marked...
Broadband Dielectric Spectroscopy on Glass-Forming Propylene Carbonate (1998)
Schneider, U., Lunkenheimer, P., Brand, R., Loidl, A.
Dielectric spectroscopy covering more than 18 decades of frequency has been performed on propylene carbonate in its liquid and supercooled-liquid state. Using quasi-optic submillimeter and...
Ionic transport and heat capacity of glass-forming metal-nitrate mixtures (1998)
Böhmer, Roland, Pimenov, A., Lunkenheimer, P., Nicklas, M., Loidl, A., Angell, C. A.
Magnetic susceptibility, heat capacity, and optical conductivity of LiPc and LiPcI (1998)
Dumm,M., Dressel,M., Nicklas,M., Lunkenheimer,P., Loidl,A., Weiden,M., ...
Magnetic susceptibility, heat capacity, and optical conductivity of LiPc and LiPcI (1998)
Dumm, M., Dressel, M., Nicklas, M., Lunkenheimer, P., Loidl, A., Weiden, M., ...
High-frequency dielectric spectroscopy of glycerol (1996)
Böhmer, Roland, Lunkenheimer, P., Pimenov, A., Schiener, B., Loidl, A.
Ion transport in the fragile glass former 3KNO3-2Ca(NO3)2 (1996)
Böhmer, Roland, Pimenov, A., Lunkenheimer, P., Rall, H., Kohlhaas, R., Loidl, A.
Fast dynamics of glass-forming glycerol studied by dielectric spectroscopy (1996)
Böhmer, Roland, Lunkenheimer, P., Pimenov, A., Dressel, M., Goncharov, Yu G., Loidl, A.
Quantum paraelectric and induced ferroelectric states in SrTiO3 (1996)
Böhmer, Roland, Hemberger, J., Nicklas, M., Viana, R., Lunkenheimer, P., Loidl, A.
Ionic motion in bioactive ceramics investigated by dielectric spectroscopy (1995)
Böhmer, Roland, Lunkenheimer, P., Alkemper, J., Fuess, H., Loidl, A.
Ionic conductivity in Li2O-Al2O3-SiO2 based glasses and glass ceramics (1995)
Böhmer, Roland, Lunkenheimer, P., Gerhard, G., Drexler, F., Loidl, A., Pannhorst, W.
Electric field dependent dielectric constant and non-linear susceptibility in SrTiO3 (1995)
Böhmer, Roland, Hemberger, J., Lunkenheimer, P., Viana, R., Loidl, A.
SrTiO3 belongs to the class of incipient ferroelectrics in which an electrically ordered state is suppressed by quantum fluctuations. To investigate the nature of these excitations, we have measured...
Dielectric relaxation dynamics in C§6§0 and C§7§0. (1995)
Mondal, P., Lunkenheimer, P., Böhmer, R., Loidl, A., Gugenberger, F., Adelmann, P., ...
Journal of Non-Crystalline Solids, 172-174(1994) S.468-71
Glassy, ceramic, and crystalline aluminosilicates (1994)
Böhmer, Roland, Lotze, M., Lunkenheimer, P., Drexler, F., Gerhard, G., Loidl, A.
Using dielectric techniques in the frequency ranges from 0.01 Hz to 1 GHz and from 60 GHz to 3 THz, the transport, relaxational and vibrational motions of Li ions in stuffed aluminosilicates were...
Dielectric spectroscopy of SrTiO3 (1994)
Böhmer, Roland, Viana, R., Lunkenheimer, P., Hemberger, J., Loidl, A.
Relaxation dynamics in C60 and C70 as studied by dielectric spectroscopy (1994)
Böhmer, Roland, Mondal, P., Lunkenheimer, P., Loidl, A., Gugenberger, F., Adelmann, P., ...
Correlated reorientations in NH4Al(SO4) · 12 H2O single crystals (1990)
Böhmer, Roland, Lunkenheimer, P., Vij, J. K., Svare, I.
Single crystals of aluminium ammonium alum NH4Al(SO4)2.12H2O were investigated using dielectric spectroscopy in the frequency range 1 kHz to 1 GHz. On approaching the ferroelectric transition at 58 K...
Department of Anesthesiology, University Hospital Gasthuisberg, Leuven, Belgium.
Radio-frequency dielectric measurements at temperatures from 10 to 450 K (1989)
Böhmer, Roland, Maglione, M., Lunkenheimer, P., Loidl, A.
A coaxial air line was constructed to connect a radio-frequency impedance analyzer and a temperature-stabilized sample holder. It is suitable for dielectric measurements in the frequency range 1...