Magnetocapacitive effect in sdw system tmtsf 2 asf 6
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Magnetocapacitive effect in SDW system (TMTSF) 2 AsF 6. D. Starešinić, D. Dominko, K. Biljaković Institute of Physics, Zagreb, Croatia P. Lunkenheimer, A. Loidl Institute of Physics, University of Augsburg, Germany. Phase diagram. new properties of SDW glass. SDW1.

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Magnetocapacitive effect in SDW system (TMTSF) 2 AsF 6

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Magnetocapacitive effect in sdw system tmtsf 2 asf 6

Magnetocapacitive effect in SDW system (TMTSF)2AsF6

D. Starešinić, D. Dominko, K. Biljaković

Institute of Physics, Zagreb, Croatia

P. Lunkenheimer, A. Loidl

Institute of Physics, University of Augsburg, Germany


Phase diagram

Phase diagram

  • new properties of SDW glass

SDW1


Low temperature sdw phase

Low temperature SDW phase

dielectric response

Lasjaunias et al. PRL 1994

thermodynamics

NMR

Takahashi et al. JPSJ 1986

also AMR, microwave response…


Multiferroic sdw

Multiferroic SDW

relaxor ferroelectric

SDW

  • SDW: incommensurate AFM + relaxor ferroelectric

  • two coexistent ferroic orders

  • possible multiferroic behaviour

Nad et al. SSC 1995

Levstik et al. PRB 1998

Betouras et al. PRL 2007


Experiments

Experiments

  • (TMTSF)2AsF6

    • very similar to (TMTSF)2PF6

  • Dielectric measurements in magnetic field

    • T down to 1.9 K

    • B up to 8 T

    • f 20 Hz – 1 MHz

  • j||a, B||c*

  • Vac=5 mV (instrument limit)

    • too low for high precision

    • too high for SDW systems (ET~10 mV/cm)

Hemberger et al. Nature 2005


Resistance

Resistance

DLT

B=8 T

DHT

B=0 T


Magnetoresistance

Magnetoresistance

  • MR roughly linear in B

  • T dependence similar to (TMTSF)2PF6

1.9 K


Dielectric constant

Dielectric constant

B=8 T

B=0 T

80 Hz

  • Similar as in (TMTSF)2PF6

  • B increases dielectric constant and relaxation time

1.6 kHz

300 kHz

300 kHz


Frequency dependence at 1 9 k

Frequency dependence at 1.9 K

8 T

Cole-Cole fit

0 T

8 T

5 T

0 T

B||b’

0 T


Parameters at 1 9 k

Parameters at 1.9 K

  • Littlewood’s pinning&screening theory does not work

  • De increases faster than the order parameter

  • B increases domain cooperativity?


Temperature vs field dependence

Temperature vs field dependence

1.9 K

1.9 K

8 T

8 T

Suggests B-T scaling!

0 T

2.9 K

8 T

1.9 K

0 T

2.9 K


Temperature dependence

Temperature dependence

8 T

0 T

8 T

0 T


Field dependence

Eact=26 K

Eact=13 K

Field dependence

1.9 K

2.6 K

1.9 K

2.6 K


Conclusions

Conclusions

  • huge magnetocapacitive effect in (TMTSF)2AsF6

  • multiferroic nature of low temperature SDW state

  • not the consequence of screening

  • no simple relation between the De(B¸,T), t(B,T) and r(B,T)

  • further measurements with better samples at lower T, lower f and lower Vac


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