我們致力於CdYb、CdMgYb和AgInMgYb準晶的製程與電性的研究。我們使用高週波法，製作出高品質的CdYb準晶。電、磁阻的量測可知CdYb準晶具有負的電阻溫度係數(dρ/dT)，而且其磁阻很小( ∆ρ(H)/ρ(T) = 0.12% 在4.2 K和6 T下)。這清楚地顯示CdYb準晶的負電阻溫度係數(dρ/dT)是由於準週期導致，因為CdYb準晶是一種單一相範圍極窄的當量化合物，以前的研究說其具有正的dρ/dT和異常巨大的磁阻是由於樣品中含有金屬Cd。高品質的CdMgYb和AgInMgYb準晶可以藉由高週波、電弧爐和單滾輪猝熄法製作，而且兩者的dρ/dT也都為負的。我們也發現老化現象會使得CdYb和CdMgYb準晶的電阻比ρ(4.2K)/ρ(300 K)變小，甚至在低溫下CdMgYb準晶的dρ/dT從負值變為正值，而AgInMgYb準晶的老化現象，似乎較為穩定。

We have studied the formation and electrical properties of CdYb, CdMgYb, and AgInMgYb quasicrystals (QCs). Using the induction melting method, we are able to prepare high quality CdYb QCs. Electrical and magnetoresistance (MR) on these CdYb QCs show that their temperature coefficient of the resistivity, dρ/dT, is negative and their MR is very small ( ∆ρ(H)/ρ(T) = 0.12% at 4.2 K and 6 T ). This clearly indicates that the negative value of dρ/dT in CdYb QCs is mainly due to the quasiperiodicity because these QCs are stoichiomeric compounds with a very narrow single phase range. Positive dρ/dT and anomalously large MR reported previously are found to be due to the existence of free Cd in the samples. It was found that high quality CdMgYb and AgInMgYb QCs can be prepared by induction melting, arc furnace, and melt spun methods and their dρ/dT is also negative. We also found that aging can reduce the resistivity ratio, ρ(4.2K)/ρ(300 K), of CdYb and CdMgYb QCs and even changes a negative dρ/dT to positive dρ/dT at low temperature for CdMgYb QCs, while subject to aging the electrical properties of AgInMgYb QCs are seen to be more stable.

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