Beata Bialek

Electronic structure of copper phthalocyanine monolayer: a first-principles study

Abstract The electronic structure of copper phthalocyanine (CuPc) monolayer was investigated by the first-principles all-electron full-potential linearized augmented plane wave (FLAPW) energy band method. The magnetic properties of the CuPc monolayer were investigated with spin-polarized calculation. It was found that the Cu atom has a magnetic moment of 0.56 μB, but it does not affect strongly the paramagnetic properties of the monolayer. The ground-state electronic structure of the CuPc monolayer found in spin-polarized calculation is indistinguishable from the paramagnetic case in the energy range from −10 to −1.5 eV and above 1.0 eV, with respect to the Fermi level (EF), but taking into account the magnetic properties of the open-shell Cu atom results with the splitting of bands near EF. The obtained total density of states and the calculated values of work function (4.66 eV) and ionization potential (5.23 eV) of the CuPc monolayer were found to be in a good agreement with the experimental data concerned CuPc thin films.

First-principles study on the electronic structures of iron phthalocyanine monolayer

The electronic band structure and magnetic properties of iron phthalocyanine (FePc) monolayer were investigated by using the first-principles all-electron full-potential linearized augmented plane wave energy band method. It is found that the ferromagnetic FePc monolayer is energetically more stable than the paramagnetic one. The exchange interaction, which splits the majority and minority bands, influences strongly on the electronic structure near the Fermi level (EF). Magnetic moment of the central Fe atom is calculated to 1.95 μB. The range of the positive polarization of Fe site is larger in the out-of-plane than in the in-plane direction. The FePc ligand remains paramagnetic. The presence of states at EF indicates the metallic character of FePc monolayer both for the paramagnetic and ferromagnetic states. However, the large density of states at EF of the majority spins in the ferromagnetic state is expected to cause a phase transition to insulating antiferromagnetic state from the metallic ferromagnetic one.

Half-metallic and Magnetic Properties of (001) Surfaces of KCaN₂ Compound in full-Heusler Structure

The electronic and the magnetic properties of (001) surface of KCaN2 half-metallic compound with full-Heusler structure are studied with the use of a full-potential linearized augmented plane wave method. Two possible terminations of the surface are considered and only the one with N atoms in the topmost layer is found to retain the half-metallic properties of the bulk. The magnetic properties of N-terminated surface are enhanced compared with the properties of the bulk. The calculated magnetic moments on the N atoms in the KCaN₂ are 1.26 μB in the bulk and 1.90 μ B at the surface. The subsurface metal atoms are also slightly polarized. In the surface terminated with metal atoms, not only the half-metallicity is destroyed, but also the magnetic properties of the system are weakened.

The Half-metallic Properties of (001) and (110) Surfaces of CsSe from the First-principles

We investigated the half-metallicity and magnetism at the (001) and (110) surfaces of CsSe in cesium chloride and zinc-blende structures by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. From the calculated local density of states, we found that all the surfaces preserve the half-metallicity of the bulk structures. The surfaces with a greater polarity have stronger ferromagnetic properties when terminated with Se atoms; the non-polar surfaces do not change their electronic or magnetic properties considerably as compared with the bulk structures.

The First-principles Calculations on the Half-metallic Properties of (001) and (110) Surfaces of Zinc-blende YC

We investigated the half-metallicity and magnetism at the (001) and (110) surfaces of YC in zinc-blende structure by using the all-electron full-potential linearized augmented plane wave method within the generalized gradient approximation. From the calculated local density of states, we found that neither (001) nor (110) surface preserves the half-metallicity. While the magnetic moment of Y atom in the YC bulk is 0.116 μB, it is 0.057 μB at the topmost layer of Y-terminated (001) surface. On the contrary, C-terminated (001) YC surface exhibits stronger magnetism than the bulk structure; the calculated magnetic moment on topmost C atom is 1.084 μB, while that of C atom in the bulk structure is 0.423 μB. The magnetic properties of the non-polar (110) YC surface are slightly enhanced as compared with the bulk structure.

Magnetic Properties and Relaxation of Vanadium Monolayer on Pd(001) Surface

We investigated the magnetism of vanadium monolayers on a Pd(001) surface. The electronic structure and the magnetic properties of the V/Pd(001) system were determined with the use of the full-potential linearized augmented plane-wave method within the general gradient approximation. Three magnetic configurations were studied: non-, ferro-, and antiferromagnetic. From the total energy calculations, we found that the V/Pd(001) system is the most stable in the antiferromagnetic configuration. The importance of relaxation on the magnetic properties of the systems was also studied. It was found that the Pd(001) surface covered with a V monolayer undergoes considerable relaxation in which the spacing between Pd layers increases in all three magnetic configurations. Contrary to the Pd interlayer spacing, the distance between the V overlayer and the topmost Pd layer is reduced. The interlayer spacing between the V overlayer and the Pd surface layer is the largest for the antiferromagnetic configuration. In the relaxed antiferromagnetic structure, the magnitude of the calculated magnetic moments on the V atoms was 1.31 μ B . The presence of the vanadium monolayer does not affect the paramagnetic properties of the Pd(001) surface.

First-principles Study on the Half-metallicity and Magnetism of the (001) Surfaces of (AlP) 1 /(CrP) 1 Superlattice

The half-metallicity and magnetism of the (001) surfaces of superlattice were investigated by means of FLAPW (Full-potential Liniarized Augmented Plane Wave) method. We considered four types of (001) surface termination, i.e., Al(S)-, Cr(S)-, P(S)Al(S-1)- and P(S)Cr(S-1)-term systems. We found that only Cr(S)-term system maintains the half-metallicity at the surface as only this system has the calculated magnetic moment of integer number of bohr magnetons. The magnetic moment of Cr(S) atom in the system was which was increased from the bulk value by the effects of band narrowing and increased spin-splitting at the surface. The electronic density of states of the P(S) atom in the P(S)Al(S-1)-term showed very sharp surface states due to the broken bonds at the surface. We found there is still a strong p-d hybridization between the P(S) and Cr(S-1) layers in the P(S)Cr(S-1)-term which causes a considerable increase of magnetic moment of P(S) atom.

호이슬러 구조 기반의 N (2-0.5n) O 0.5n KCa (n = 0~4) 화합물의 반쪽금속성 및 자성에 대한 제일원리 연구

최근에 발견된 d? 반쪽금속성을 가지는 호이슬러 화합물 N₃KCa와 O₂KCa이 합금을 이루었을 때 그 반쪽금속성과 자성을 제일원리 방법을 이용하여 연구하였다. 계산을 통해 얻은 상태밀도와 총 자기모멘트를 통해 고려의 대상인 N 1.5 O 0.5 KCa, NOKCa, N 0.5 O 1.5 KCa 등 세 가지 화합물 모두 반쪽금속성 나타냄을 알 수 있었다. 이들 화합물에서 N 원자와 O 원자의 자기모멘트는 순수물질에 비해 상당히 증가하였으며, K 원자의 자기모멘트는 상당히 큰 음의 값을 가졌다. 각 원자들의 자기모멘트와 계산된 원자별 상태밀도를 연관시켜 자성과 반쪽금속성을 논의하였다.

Electronic Structures and Magnetism at the Interfaces of Rocksalt Structured Half-metallic NaN and CaN

Magnetism at the interfaces of rocksalt structured half-metals, NaN and CaN were investigated by use of the first-principles band calculations. The electronic structures for the simple interface and mixed interface systems were calculated by the FLAPW (full-potential linearized augmented plane wave) method. From the calculated number of electrons in muffin-tin spheres of each atom, we found, for the simple interface system, that the magnetic moment of the N atom in the CaN (NaN) side is increased (decreased) compared to those of inner N atoms. For the mixed interface system, the magnetic moments of the interface N atoms are similar to the averaged value for the inner N atoms in CaN and NaN side. Among four interface N atoms, the N atom connected to Na atoms in the upper and down layers has the largest magnetic moment and that connected to Ca atoms has the smallest. The number of p electrons in each N atom and the calculated density of states explain well the above situation.

Half-metallicity at the Surfaces of Rocksalt and Zinc-blende Sodium Nitride

Compounds such as NaN belong to an interesting class of materials in which a magnetic order may appear despite the lack of d electrons. The magnetic properties of these materials are ascribed to the partially filled p shells. Recently, on the basis of electronic structure calculations from first principles, it has been found that NaN is a ferromagnetic half-metal in rocksalt (RS) and zinc-blende (ZB) structures with half-metallic band gaps in majority electron channels. The former structure has appeared to be more stable. From the first-principles calculation, we found that the half-metallic properties of the bulk RS and ZB NaN are conserved at the RS(001) and ZB(110) surfaces. Due to the interactions between Na s and N p electrons, N atoms become positively polarized. In the RS NaN (001) the calculated values of the magnetic moments of the N atoms is about . The magnetic moment on the N atom in the top most layer of ZB(110) is slightly larger than that of the RS(001) surface, i.e., . The Na atoms in the both structure are hardly polarized.