TY - JOUR AU - Csősz, Gábor AU - Márkus, Bence Gábor AU - Jánossy, András AU - Nemes, NM AU - Muranyi, F AU - Pergerné Klupp, Gyöngyi AU - Kamarás, Katalin AU - Kogan, VG AU - Bud'ko, SL AU - Canfield, PC AU - Simon, Ferenc TI - Giant microwave absorption in fine powders of superconductors JF - SCIENTIFIC REPORTS J2 - SCI REP VL - 8 PY - 2018 PG - 9 SN - 2045-2322 DO - 10.1038/s41598-018-29750-7 UR - https://m2.mtmt.hu/api/publication/3403957 ID - 3403957 LA - English DB - MTMT ER - TY - JOUR AU - Náfrádi, Bálint AU - Antal, Ágnes AU - Fehér, Titusz AU - Kiss, László Ferenc AU - Mézière, C AU - Batail, P AU - Forró, L AU - Jánossy, András TI - Frustration-induced one-dimensionality in the isosceles triangular antiferromagnetic lattice of δ -(EDT-TTF- CONMe2)2AsF6 JF - PHYSICAL REVIEW B J2 - PHYS REV B VL - 94 PY - 2016 IS - 17 PG - 6 SN - 2469-9950 DO - 10.1103/PhysRevB.94.174413 UR - https://m2.mtmt.hu/api/publication/3141160 ID - 3141160 LA - English DB - MTMT ER - TY - JOUR AU - Quintavalle, Dario AU - Márkus, Bence Gábor AU - Jánossy, András AU - Simon, Ferenc AU - Pergerné Klupp, Gyöngyi AU - Gyori, MA AU - Kamarás, Katalin AU - Magnani, G AU - Pontiroli, D AU - Riccò, M TI - Electronic and ionic conductivities in superionic Li4 C60 JF - PHYSICAL REVIEW B J2 - PHYS REV B VL - 93 PY - 2016 IS - 20 PG - 8 SN - 2469-9950 DO - 10.1103/PhysRevB.93.205103 UR - https://m2.mtmt.hu/api/publication/3067673 ID - 3067673 LA - English DB - MTMT ER - TY - JOUR AU - Antal, Ágnes AU - Fehér, Titusz AU - Náfrádi, Bálint AU - Forro, L AU - Jánossy, András TI - Two-dimensional Magnetism in kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl, a Spin-1/2 Heisenberg Antiferromagnet with Dzyaloshinskii-Moriya Interaction JF - JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN J2 - J PHYS SOC JPN VL - 84 PY - 2015 IS - 12 PG - 6 SN - 0031-9015 DO - 10.7566/JPSJ.84.124704 UR - https://m2.mtmt.hu/api/publication/3000542 ID - 3000542 N1 - Funding Agency and Grant Number: Hungarian National Research FundOrszagos Tudomanyos Kutatasi Alapprogramok (OTKA) [OTKA K107228] Funding text: We are indebted to Professor F. Mila (EPFL) for stimulating discussions and acknowledge the Hungarian National Research Fund OTKA K107228 and the Swiss NSF and its NCCR "MaNEP". Department of Physics, Budapest University of Technology and Economics, Budafoki út 8, Budapest, H-1111, Hungary Department of Physics, Budapest University of Technology and Economics, MTA-BME Condensed Matter Research Group, MTA-BME Lendület Magneteo-optical Research Group, Budafoki út 8, Budapest, H-1111, Hungary Institute of Physics of Complex Matter, FBS, Swiss Federal Institute of Technology (EPFL), Lausanne, CH-1015, Switzerland Cited By :3 Export Date: 4 May 2020 CODEN: JUPSA Department of Physics, Budapest University of Technology and Economics, Budafoki út 8, Budapest, H-1111, Hungary Department of Physics, Budapest University of Technology and Economics, MTA-BME Condensed Matter Research Group, MTA-BME Lendület Magneteo-optical Research Group, Budafoki út 8, Budapest, H-1111, Hungary Institute of Physics of Complex Matter, FBS, Swiss Federal Institute of Technology (EPFL), Lausanne, CH-1015, Switzerland Cited By :7 Export Date: 17 May 2021 CODEN: JUPSA AB - The finite phase transition temperature, T-N, of quasi two-dimensional (2D) Heisenberg antiferromagnetic (AF) crystals results from in-plane anisotropy or coupling between layers. It is usually not known which is the determining factor when both are weak. We show by an electron spin resonance experiment that in the quasi 2D antiferromagnetic crystal,kappa-(BEDT-TTF)(2)Cu[N(CN)(2)] Cl, TN is determined by in-plane anisotropy while interlayer coupling plays a minor role. The compound has a large isotropic Heisenberg exchange interaction between sites with S = 1/2 spins. The Dzyaloshinskii-Moriya (DM) interaction is the main source of anisotropy, while in-plane anisotropy and the interlayer coupling are very weak. The external-field field-induced static and fluctuating AF magnetizations are independent in adjacent layers above the (zero-field) ordering temperature. LA - English DB - MTMT ER - TY - JOUR AU - Jánossy, András TI - Fullerének: szépség és hasznosság JF - MAGYAR TUDOMÁNY J2 - MAGYAR TUDOMÁNY VL - 174 PY - 2013 IS - 9 SP - 1103 EP - 1110 PG - 8 SN - 0025-0325 UR - https://m2.mtmt.hu/api/publication/2695807 ID - 2695807 LA - Hungarian DB - MTMT ER - TY - JOUR AU - Náfrádi, B AU - Antal, Ágnes AU - Pásztor, Á AU - Forró, L AU - Kiss, László Ferenc AU - Fehér, Titusz AU - Kováts, Éva AU - Pekker, Sándor AU - Jánossy, András TI - Molecular and spin dynamics in the paramagnetic endohedral fullerene Gd 3N@C 80 JF - JOURNAL OF PHYSICAL CHEMISTRY LETTERS J2 - J PHYS CHEM LETT VL - 3 PY - 2012 IS - 22 SP - 3291 EP - 3296 PG - 6 SN - 1948-7185 DO - 10.1021/jz301250j UR - https://m2.mtmt.hu/api/publication/2137109 ID - 2137109 LA - English DB - MTMT ER - TY - JOUR AU - Antal, Ágnes AU - Fehér, Titusz AU - Nafradi, B AU - Forro, L AU - Jánossy, András TI - Magnetic fluctuations above the Neel temperature in kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl, a quasi-2D Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interaction JF - PHYSICA STATUS SOLIDI B-BASIC RESEARCH J2 - PHYS STAT SOL B BASIC RES VL - 249 PY - 2012 IS - 5 SP - 1004 EP - 1007 PG - 4 SN - 0370-1972 DO - 10.1002/pssb.201100731 UR - https://m2.mtmt.hu/api/publication/2111396 ID - 2111396 LA - English DB - MTMT ER - TY - JOUR AU - Penc, Karlo AU - Romhányi, Judit AU - Rõõm, T AU - Nagel, U AU - Antal, Ágnes AU - Fehér, Titusz AU - Jánossy, András AU - Engelkamp, H AU - Murakawa, H AU - Tokura, Y AU - Szaller, Dávid AU - Bordács, Sándor AU - Kézsmárki, István TI - Spin-Stretching Modes in Anisotropic Magnets: Spin-Wave Excitations in the Multiferroic Ba2CoGe2O7 JF - PHYSICAL REVIEW LETTERS J2 - PHYS REV LETT VL - 108 PY - 2012 IS - 25 PG - 5 SN - 0031-9007 DO - 10.1103/PhysRevLett.108.257203 UR - https://m2.mtmt.hu/api/publication/1996782 ID - 1996782 AB - We studied spin excitations in the magnetically ordered phase of the noncentrosymmetric Ba2CoGe2O7 in high magnetic fields up to 33 T. In the electron spin resonance and far infrared absorption spectra we found several spin excitations beyond the two conventional magnon modes expected for such a two- sublattice antiferromagnet. We show that a multiboson spin-wave theory describes these unconventional modes, including spin-stretching modes, characterized by an oscillating magnetic dipole and quadrupole moment. The lack of inversion symmetry allows each mode to become electric dipole active. We expect that the spin-stretching modes can be generally observed in inelastic neutron scattering and light absorption experiments in a broad class of ordered S > 1/2 spin systems with strong single-ion anisotropy and/or noncentrosymmetric lattice structure. LA - English DB - MTMT ER - TY - JOUR AU - Antal, Ágnes AU - Fehér, Titusz AU - Tátrainé Szekeres, Erzsébet AU - Fülöp, Ferenc AU - Náfrádi, Bálint AU - Forro, L AU - Jánossy, András TI - Pressure and temperature dependence of interlayer spin diffusion and electrical conductivity in the layered organic conductors kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]X (X = Cl, Br) JF - PHYSICAL REVIEW B J2 - PHYS REV B VL - 84 PY - 2011 IS - 7 PG - 9 SN - 2469-9950 DO - 10.1103/PhysRevB.84.075124 UR - https://m2.mtmt.hu/api/publication/1847933 ID - 1847933 N1 - Funding Agency and Grant Number: Hungarian National Research FundOrszagos Tudomanyos Kutatasi Alapprogramok (OTKA) [OTKA PF63954, K68807, NN76727]; Swiss NSFSwiss National Science Foundation (SNSF); Swiss NCCR "MaNEP"; New Hungary Development Plan [TAMOP-4.2.1/B-09/1/KMR-2010-0002]; Hungarian Academy of SciencesHungarian Academy of Sciences Funding text: We are indebted to N. D. Kushch (Institute of Problems of Chemical Physics, Chernogolovka, Russia) for instructions on crystal growth, to M. Czugler and V. Kudar (Chemical Research Institute Budapest) for x-ray and to K. Vad (ATOMKI) for secondary neutral mass spectrometry characterization of crystals and to R. Gaal (EPFL) for resistivity measurements. This work was supported by the Hungarian National Research Fund OTKA PF63954, K68807, NN76727, the Swiss NSF and its NCCR "MaNEP" and the New Hungary Development Plan TAMOP-4.2.1/B-09/1/KMR-2010-0002. T. F. acknowledges support from the Janos Bolyai program of the Hungarian Academy of Sciences. Budapest University of Technology and Economics, Institute of Physics and Condensed Matter Research Group, Hungarian Academy of Sciences, P.O. Box 91, H-1521 Budapest, Hungary Institute of Physics of Complex Matter, FBS, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland Cited By :14 Export Date: 4 May 2020 CODEN: PRBMD Correspondence Address: Antal, Á.; Budapest University of Technology and Economics, Institute of Physics and Condensed Matter Research Group, Hungarian Academy of Sciences, P.O. Box 91, H-1521 Budapest, Hungary Budapest University of Technology and Economics, Institute of Physics and Condensed Matter Research Group, Hungarian Academy of Sciences, P.O. Box 91, H-1521 Budapest, Hungary Institute of Physics of Complex Matter, FBS, Swiss Federal Institute of Technology (EPFL), CH-1015 Lausanne, Switzerland Cited By :16 Export Date: 17 May 2021 CODEN: PRBMD Correspondence Address: Antal, Á.; Budapest University of Technology and Economics, P.O. Box 91, H-1521 Budapest, Hungary AB - A high frequency (111.2-420 GHz) electron spin resonance study of the interlayer spin diffusion is presented in the conducting phases of the layered organic compounds, kappa-( BEDT-TTF)(2)Cu[N(CN)(2)]X (kappa-ET(2)-X), X = Cl or Br. The interlayer spin cross relaxation time T(x) and the intrinsic spin relaxation time T(2) of single layers are measured as a function of temperature and pressure. Spin diffusion is two dimensional in the high temperature bad-metal phase (i.e., electrons are confined to a single molecular layer for longer than T(2)). The interlayer electron hopping frequency nu(perpendicular to) = 1/(2T(x)) decreases along the bad-metal to Mott insulator crossover and increases along the bad-metal to normal metal (or superconductor) crossover. The density of states (DOS) is determined from a comparison of T(x) and the interlayer resistivity. In the bad-metal phase it is four to five times larger than the DOS calculated from the electronic structure neglecting electron correlations. In kappa-ET(2)-X the DOS increases with pressure along the bad-metal to normal metal crossover. Results are compared with predictions of the dynamical mean field theory. LA - English DB - MTMT ER - TY - JOUR AU - Nagy, Kálmán AU - Quintavalle, Dario AU - Fehér, Titusz AU - Jánossy, András TI - Multipurpose High-Frequency ESR Spectrometer for Condensed Matter Research JF - APPLIED MAGNETIC RESONANCE J2 - APPL MAGN RESON VL - 40 PY - 2011 IS - 1 SP - 47 EP - 63 PG - 17 SN - 0937-9347 DO - 10.1007/s00723-010-0182-4 UR - https://m2.mtmt.hu/api/publication/1446535 ID - 1446535 N1 - Funding Agency and Grant Number: Hungarian National Research Fund OTKA [NK-60984, PF-63954, K-68807, NN-76727]; New Hungary Development Plan [TAMOP-4.2.1/B-09/1/KMR-2010-0002]; Hungarian Academy of Sciences Funding text: We thank Richard Wylde for his help in designing the spectrometer and Laszlo Forro for sharing his experience and enabling us to use his laboratory. This work was supported by the Hungarian National Research Fund OTKA NK-60984, PF-63954, K-68807, NN-76727. We acknowledge support by the New Hungary Development Plan, TAMOP-4.2.1/B-09/1/KMR-2010-0002. T.F. acknowledges financial support from the Janos Bolyai program of the Hungarian Academy of Sciences. LA - English DB - MTMT ER -