Journal of the Korean Magnetics Society (한국자기학회지)

The Korean Magnetics Society (한국자기학회)
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The Electronic Structure and Magnetism of bcc Rh(001) Surface

체심 입방구조 Rh(001) 표면의 전자구조와 자성

  • Cho, L.H. (Department of Physics, Inha University) ;
  • Bialek, B. (Department of Physics, Inha University) ;
  • Lee, J.I. (Department of Physics, Inha University)
  • Published : 2008.12.31
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Abstract

According to the recent reports the bulk bcc Rh is ferromagnetic with a small difference of energy compared to paramagnetic state. In this study, the electronic structure and magnetism for bcc Rh(001) surface are investigated by means of the all-electron full potential linearized augmented plane wave method within the generalized gradient approximation. It is found that the surface ferromagnetic state is preferable over the paramagnetic one. For unrelaxed system, the magnetic moment of the surface layer, $0.48{\mu}B$, is slightly increased comparing with the bulk value, $0.41{\mu}B$ while the value of the subsurface layer, $0.23{\mu}B$, is much smaller than the bulk value. The total energy and atomic force calculations show that the surface layer is relaxed downward and the subsurface layer moves upward to reduce the layer distance between the surface and subsurface layers by 7.0 %. The relaxation effect leads to weakening the surface magnetic properties. Specifically, the value of the magnetic moment of the surface atom is decreased to $0.36{\mu}B$. Since the spin polarization of the subsurface layer is only $0.14{\mu}B$, it is concluded that the bcc Rh(001) surface is rather weakly ferromagnetic.

최근의 연구에 따르면 체심입방구조(bcc)를 가지는 Rh은 상자성 상태와 약간의 에너지 차를 보이며 강자성체가 된다고 한다. 이 연구에서는 bcc Rh(001) 표면의 전자구조와 자성을 일반기울기 근사 하에서 총퍼텐셜 선형보강 평면파 에너지 띠 계산방법을 이용하여 연구하였다. 표면의 자성상태는 강자성상태를 가졌으며, unrelaxed 된 경우에 표면층의 자기모멘트는 $0.48{\mu}B$로 덩치상태의 $0.43{\mu}B$에 비해 증진되었으나, 표면 바로 밑층의 자기모멘트는 $0.23{\mu}B$으로 상당히 줄어들었다. 총에너지 및 원자힘 계산을 통해 relaxed 된 구조를 구하였는데, 이 때 표면 층은 안쪽으로, 표면 바로 밑층은 바깥 쪽으로 이동하여 원래의 층간격보다 약 7.0% 줄어들었다. 이러한 층간 간격 변화는 표면 자성을 약화시켜, 표면층과 표면 바로 밑층의 자기모멘트를 $0.36{\mu}B$ 및 $0.14{\mu}B$로 줄어들게 하였다.

Keywords

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