Ultrasonic Investigation on the Distorted Diamond Chain Substance Azurite P T Cong1, B Wolf1, U Tutsch1, K Remović-Langer1, J Schreuer2, S Süllow3, and Meters Lang1 one particular Physikalisches Institut, Universität Holland, SFB/TR49, 60438 Frankfurt(M) two Institut für Mineralogie, Ruhr- Universität, 44780 Bochum a few Institut für Physik dieser Kondensierten Fall, TU Braunschweig, 38106 Braunschweig
E-mail: [email protected] uni-frankfurt. de
Fuzy. The natural mineral Azurite [Cu3(CO3)2(OH)2] have been considered as an auto dvd unit substance for the 1D distorted antiferromagnetic diamond cycle, the minute couplings that, however , are still under debate. Here all of us present benefits of the longitudinal elastic frequent c22 right down to 80 mK and magnetic fields up to 12 Capital t. c22 uncovers clear validations of the magnet energy weighing scales involved and discloses distinctive anomalies at the Néel purchasing TN sama dengan 1 . 88 K. Depending on measurement as being a function of temperature and magnetic field, a detailed B-T phase diagram is planned out which includes one more phase boundary of unknown origin at low temperature (T < 0. 5 K). Entering the newest phase is usually accompanied by a obvious softening with the c22 elastic constant. These observations, together with results obtained by spectroscopic investigations reported in the literature, reflect an unusual long-range magnetically ordered point out at really low temperatures.
Low-dimensional (low-D) quantum spin systems are of great interest in solid point out physics because of the wealth of exciting phenomena from the interplay of decreased dimensionality, contending interactions and strong quantum fluctuations. Recently, great fascination and controversy has surrounded the pitch that the spin S = 1/2 occasions of the Cu2+ ions in azurite [Cu3(CO3)2(OH)2] form a frustrated 1D distorted diamond chain [1-3]. The magnetic structure of azurite and the relevant microscopic couplings, however , have been completely disputed at experimental and theoretical research [4-6]. In addition , the detailed phase diagram at low temperature and high permanent magnetic fields continues to be unknown plus some recent experiments suggest that there exists a more complicated micromagnetic structure than has recently been believed [7, 8].
Results and Debate
Using a phase-sensitive detection technique, we have scored the comparable change with the velocity of your longitudinal ultrasonic wave propagating along the spin-chain direction (b axis) of your high-quality one crystal of azurite. This kind of geometry compares to the c22 acoustic mode. The elastic constant could be calculated from the sound speed ν and the crystal's mass density ρ by c22 = ρν2. |[pic] | |Figure 1 . a) Heat dependence of the longitudinal c22 acoustic mode for B = 0 T (left scale) and the permanent magnet susceptibility | |χmol(T) (right scale) drawn on the same temperature axis.
Measurements have been performed both as a function of heat and permanent magnet field. The external discipline was applied either verticle with respect or parallel to the n axis.
Determine 1 displays the temperature dependence of c22 alongside the molar magnet susceptibility χmol. The latter continues to be determined by using a homemade SQUID magnetometer. At TN sama dengan 1 . 88 K we observed in equally curves a pronounced abnormality - a baseline in c22(T) coinciding which has a sharp twist in χ(T) - showing long-range antiferromagnetic ordering. The dimensions of the flexible anomaly (of the order of 0. 1%) is definitely typical pertaining to an antiferromagnetic (AFM) move. A surprising end result obtained from the ultrasonic measurements is the observation of an additional pronounced softening of c22. The onset of this treatment coincides with an abrupt increase of χmol(T) pertaining to T < 0. forty five K. Note that...
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