Critical behavior and spin dynamics of Heisenberg antiferromagnetic spin chains in high magnetic fields
Final Report Abstract
The research program of the project aimed to test recent theoretical predictions focused on understanding magnetic properties of low-dimensional quantum magnets in high magnetic fields. Among the most significant achievements are (i) the observation of a transition from the sine-Gordon region (with soliton-breather elementary excitations) to a spin-polarized state (with magnon excitations) in copper pyrimidine dinitrate, a spin-1/2 antiferromagnetic chain with alternating g-tensor and Dzyaloshinskii-Moriya interactions that exhibits a field-induced spin gap; (ii) the observation of two modes with asymmetric frequency-field dependences in the spin-1/2 chain compound (C6H9N2)CuCl3 [known as (6MAP)CuCl3], illuminating the striking incompatibility with a simple uniform S=1/2 Heisenberg chain model employed for this compound previously, and, based on a developed theory, suggesting the important role of next-nearest-neighbor interactions in (6MAP)CuCl3; (iii) the demonstration of successful use of picosecond-pulse freeelectron-laser radiation for the continuous-wave THz-range electron spin resonance (ESR) spectroscopy in magnetic fields up to ca 70 T. This technique appears to be very important for studying ESR excitations in low-dimensional quantum spin systems in the THz frequency range; (iv) the systematic study of the low-energy excitation spectrum in the magnon BEC candidate compound (NiCl2-4SC(NH2)2 [known as DTN] in the fieldinduced magnetically ordered phase. Two observed gapped modes are consistently interpreted within a four-sublattice antiferromagnet model with a finite interaction between two tetragonal subsystems and unbroken axial symmetry; (v) the direct evidence for a biaxial anisotropy (~5% of the dominant exchange interaction) in the spin-ladder material (C5H12N)2CuBr4 [known as BPCB] caused by a substantial spinorbit coupling, that is in contrast to a fully isotropic spin-ladder model employed for this system previously; (vi) the conclusive description of the parameters of the spin Hamiltonian of the quasi-two-dimensional spin-1/2 Heisenberg antiferromagnet [Cu(pyz)2(HF2)]PF6, allowing us to accurately describe the unusual phase diagram of this material.
Publications
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Magnetic properties of the Haldane-gap material [Ni(C2H8N2)2NO2](BF4), New J. of Physics 10, 033008, 2008
E. Čižmár, M. Ozerov, O. Ignatchik, T.P. Papageorgiou, J. Wosnitza, S.A. Zvyagin, J. Krzystek, Z. Zhou, C.P. Landee, B.R. Landry, M.M. Thurnbull, and J.L. Wikara
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Spin dynamics of NiCl2-4SC(NH2)2 in the field-induced ordered phase, Phys. Rev. B 77, 092413, 2008
S.A. Zvyagin, J. Wosnitza, A.K. Kolezhuk, V.S. Zapf, M. Jaime, A. Paduan-Filho, V.N. Glazkov, S.S. Sosin, and A.I. Smirnov
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Terahertz-range free-electron laser electron spin resonance spectroscopy: Techniques and applications in high magnetic fields, Rev. Sci. Instr. 80, 073102, 2009
S.A. Zvyagin, M. Ozerov, E. Čižmár, D. Kamenskyi, S. Zherlistyn, T. Herrmannsdörfer, J. Wosnitza, R. Wünsch, and W. Seidel
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Anisotropy of magnetic interactions in the spin-ladder compound (C5H12N)2CuBr4, Phys. Rev. B 82, 054431, 2010
E. Čižmár, M. Ozerov, J. Wosnitza, B. Thielemann, K. W. Krämer, Ch. Rüegg, O. Piovesana, M. Klanjšek, M. Horvatić, C. Berthier, and S. A. Zvyagin
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Magnetic properties of the quasi-two-dimensional S=1/2 Heisenberg antiferromagnet [Cu(pyz)2(HF2)]PF6, Phys. Rev. B 81, 064422, 2010
E. Čižmár, S.A. Zvyagin, R. Beyer, M. Uhlarz, M. Ozerov, Y. Skourski, J.L. Manson, J.A. Schlueter, and J. Wosnitza
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Spin dynamics in S=1/2 chains with next-nearest-neighbor exchange interactions, Phys. Rev. B 82, 014416, 2010
M. Ozerov, A.A. Zvyagin, E. Čižmár, J. Wosnitza, R. Feyerherm, F. Xiao, C. P. Landee, and S. A. Zvyagin
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Field-induced gap in a quantum spin-1/2 chain in a strong magnetic field, Phys. Rev. B 83, 060409(R), 2011
S.A. Zvyagin, E. Čižmár, M. Ozerov, J. Wosnitza, R. Feyerherm, S.R. Manmana, and F. Mila
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High-field electron spin resonance in low-dimensional spin systems, Ph. D. Thesis, 2011
Mykhaylo Ozerov
