Novel Phase Transition in Spin-1/2 Linear Chain Systems: NaTiSi₂O₆and LiTiSi₂O₆

Direct measurement of the spin gap in a quasi-one-dimensional clinopyroxene:NaTiSi2O6

“…A broad feature appearing in the magnetic susceptibility and heat capacity at 210 K indicates a phase transition typical of Spin-Peierls materials, but the transition occurs at higher temperatures than predicted by the Bonner-Fisher equation 2 . This implies that simple magnetic fluctuations are not strong enough to induce spin-pairing.…”

“…Figure 3d shows the magnetic susceptibility of NaTiSi 2 O 6 with a Curie-law correction at lowtemperatures used to correct for the susceptibility or unpaired "stray" spins 2 . The susceptibility was measured between 2 and 350 K. The Curie-law correction appears to fail at temperatures lower than 30 K as compared to the original susceptibility measurements made by Isobe et al 2 . This is most likely due to their use of a Superconducting Quantum Interference Device (SQUID) magnetometer, which is far more sensitive than a VSM.…”

“…Previous experiments on NaTiSi 2 O 6 have been numerous [1][2][3][4][5][7][8][9][10] . A broad feature appearing in the magnetic susceptibility and heat capacity at 210 K indicates a phase transition typical of Spin-Peierls materials, but the transition occurs at higher temperatures than predicted by the Bonner-Fisher equation 2 .…”

“…This implies that simple magnetic fluctuations are not strong enough to induce spin-pairing. On the other hand, it was noticed that Ti 3+ dimerization occurs as the system transitions from C 2/c to the P1 space group at lower temperatures with no new magnetic Bragg peaks 2,3,7,10 . Raman and infrared spectroscopy show broadness in the phonon frequencies that split and sharpen not only as the temperature is lowered, but also as Ti 3+ is substituted for higher spin ions like V 3+ and Cr 3+8 .…”

Magnetic and crystal structures of the one-dimensional ferromagnetic chain pyroxeneNaCrGe2O6

“…6͒ or the low-dimensional magnetism found in LiVGe 2 O 6 . 7 While these pyroxenes have been the subject of various studies, [5][6][7][8][9][10][11][12] the complete magnetic structures are known only for few members of this class. 7,[11][12][13][14][15] We have started recently to investigate the magnetic structure of several pyroxene materials.…”