MnxSi的比熱與磁性

Abstract

我們對一系列不同Mn含量的MnxSi單晶進行比熱量測，Mn含量分別為x = 0.998、0.981、0.961、0.945。我們根據量測到的數據，將相變特徵分為兩類：一種為單一峰值的相變特徵；另外一種相變特徵的結構則是在低溫處有一尖峰，在高溫處伴隨一個寬峰。 藉由Debye模型擬合100 K 到200 K的數據計算出樣品的γ值和Debye溫度，扣除了樣品電子比熱和晶格比熱的貢獻得到比熱的磁性貢獻，進而計算出兩類樣品的磁性熵值差異。 與LiCu2O2樣品比熱量測結果的比較，配合S.W. Huang et al. (Physical Review Letters 101, 077205(2008) ) 對LiCu2O2磁性結構探測結果與提出的模型以及S.V. Grigoriev et al. (Physical Review B 79, 144417(2009) ) 的理論模型跟A. Bauer et al. (Physical Review B 85, 214418(2012) ) 的研究，我們試著討論MnSi相變特徵在高溫處的寬峰結構。

We have measured the specific heat of MnxSi single crystals with the various manganese contents (x = 0.998, 0.981, 0.961, 0.945). We classified the magnetic transition features. The first kind has only one peak. The other kind have one sharp peak and a broad peak at higher temperature. The Debye temperatures and the γ have been calculated by fitting the specific heat from 100 K to 200 K. We subtract the electron and phonon contributions to obtain the purely magnetic contribution. Then, we calculated the magnetic entropy difference between these two types of compounds. We compared current results to the specific heat of the LiCu2O2 and the magnetic structure model provide by S.W. Huang et al. (Physical Review Letters 101, 077205(2008) ) and to the study of MnSi by S.V. Grigoriev et al.(Physical Review B 79, 144417(2009) ) and A. Bauer et al.(Physical Review B 85, 214418(2012) ). We discuss what physical mechanism is in the magnetic transitions.