| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2002: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
We have studied(i)how the power law holds over wide tempetarwe range inAFphase, revealing that the gxnwth exponent n-02 is almost temperature independent and the pie-factor Cis temperature dependent so that C(T)can be fitted to C_0exp(-dE/k_BT)with a kind of activation energy dE/k_B〜10 K and(ii)domain-growth-kineucs in Ferri-magetic phase at H_s=1300 Oe where A'C'-type domain wall is considered to move almost freely and the time evolution of magnetic suscepbblity c' shows power law c'(t)=c'_<eq>+At^n with n〜02.(iii)preserving anomalously low giowdi exponent n〜0.2, anisotropic pinning effect on domain-wall-motion by non-magnetic impunity was clearly observed for the sample with x=0.005. As anisotiopic suppression of domain growth under extemally applied magnetic field in the sample with x=0.00 has been explained, this anisotiopic pinning effect for domain-wail-motion by non-magnetic impurity can be explained by activation energy consideration ; theA/D-type domain wall motion in the b diiection, which is dominated by the stochastic reversal of free magnetic chains due to the isosceles tnangularlauice geomeby of CoNb2O6, is easily disturbed by non-magnetic impurity, while the domain wall motion in the a diiection is not because all sites have finite activation energy.(iiii)only 1% substitution is enough to suppress the domain-growth-kinetics in this system.(In the H_<//c>-T magnetic phase diagram of the sample with x=0.01, as a consequence of suppression of the domain-growth-kinetics, an apparent incommensurate(IC)state, in which thermodynamically equivalent four types of AF domains, A, B, C, D, arrange quasi-regularly along the b axis(likeA/D/C/B/A/D...)with phase shift of π/2, replaces AF state seen in the sample with x=0.00 as low temperature state, maintaining shape of the magnetic phase boundaries.
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