• Journal of Magnetics
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• 제3권4호
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• pp.105-111
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• 1998

The low energy excitations of spin waves (SWR) in thin films can be used for determination of the surface anisotropy constant and the nonhomogeneities of magnetization in the close-to-surface layer. The dispersion relation in SWR is sensitive on the geometry of experiment. We report on temperature dependence of surface magnetic anisotropy energy constant in magnetic semiconductor thin films of$ CdCr_{2-2x}In_{2x}Se_4$ at spin glass state. Samples were deposited by rf sputtering technique on Corning glass substrate in controlled temperature conditions. Coexistence of the infinite ferromagnetic network (IFN) and finite spin slusters (FSC) in spin glass state (SG) is know phenomena. Some behavior typical for long range magnetic ordering is expected in samples at SG state. The spin wave resonance experiment (microwave spectrometer at X-band) with excited surface modes was applied to describe the energy state of surface spins. We determined the surface magnetic anisotropy energy constant versus temperature using the surface inhomogeneities model of magnetic thin films. It was found that two components contribute to the surface magnetic anisotropy energy. One originates from the exchange interaction term due to the lack of translation symmetry for surface spin as well as from the originates from the exchange interaction term due to the lack of translation symmetry for surface spin as well as from the stray field of the surface roughness. The second one comes from the demagnetizing field of close-to surface layer with grad M. Both term linearly decrease when temperature is increased from 5 to 123 K, but dominant contribution is from the first component.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.61-61
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• 2011

Using ab initio calculations, we study the MgO(001) and Fe/MgO(001) surface phases and the effects of interface structure on the Fe/MgO magnetic anisotropy. The surface phase diagrams of MgO(001) and Fe/MgO(001) show that the most stable surface structures are either defect-free surface or the surfaces with oxygen vacancies in c($2{\times}1$) periodicity for the systems. By the formations of the oxygen vacancy rows on MgO(001) surface, the in-plane magnetic anisotropy energy of Fe overlayer is reduced while the perpendicular magnetic anisotropy energy is increased from 0.1 to 0.5 meV per Fe atom.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.314-314
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• 2011

Using first principles calculations, we investigated the interface structure effects on the magnetic properties of the Fe/BaTiO3 system. On the BaO-terminated surface, a Fe monolayer is formed as two Fe atoms are adsorbed on the top sites of Ba and O in the ($1{\times}1$) surface unit and a Fe ML is formed on the TiO2-terminated surface as two Fe atoms are adsorbed on the two O top sites. The magnetic anisotropy energy of Fe was higher on the TiO2?-erminated surface (1.5 eV) than on the BaO-terminated surface (0.5 eV). The decomposed electron density of the states showed that the stronger hybridization of Fe with the TiO2 layer than with the BaO layer is the most important reason for the higher magnetic anisotropy energy.

• 한국전기전자재료학회논문지
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• 제16권3호
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• pp.238-246
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• 2003

We have performed the simulation of ferromagnetic resonance spectra on the exchange coupled bilayer thin films at perpendicular configuration. Variables considered in spectrum calculation were the interfacial exchange constants per unit area, the layer thickness, and the surface anisotropy constants. In case of antiferromagnetic coupling, variation of exchange constant gave a great effect to the absorption spectra of the low and the high magnetization layer. Variation of thickness in low magnetization layer did nt nearly influenced the resonated field of the high magnetization layer. Also, the increase of negative surface anisotropy increased the resonance field of the low and the high magnetization layer.

• 한국자기학회지
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• 제5권5호
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• pp.461-464
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• 1995

We have investigated the effects of sputtering Ar gas pressure on magnetic anisotropy of Co/Pt multilayers, where sputtering Ar gas pressure was varied from 2 to 20 mTorr. The surface and volume anisotropies were found to be strongly dependent on sputtering Ar gas pressure. In particular, the surface anisotropy exhibited more than fourfold enhancement as Ar pressure was decreased from 20 to 5 mTorr. We have found that the surface anisotropy was closely correlated with the low-angle x-ray diffraction intensity. We believe that these results are mainly ascribed to the variation of microstructure in the Co/Pt multilayer thin films with sputtering Ar gas pressure.

• Journal of Magnetics
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• 제7권3호
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• pp.80-93
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• 2002

The role of magnetic anisotropy of the antiferromagnetic layer on the magnetization process of exchange coupled polycrystalline ferromagnetidantiferromagnetic bilayers is discussed. In order to elucidate the magnetic torque response of Ni-Fe/Mn-Ir bilayers, the single spin ensemble model is newly introduced, taking into account the two-dimensionally random distribution of the magnetic anisotropy axes of the antiferromagnetic grains. The mechanism of the reversible inducement of the exchange anisotropy along desirable directions by field cooling procedure is successfully explained with the new model. Unidirectional anisotropy constant, J$k$, of polycrystalline Ni-Fe/Mn-Ir and Co-Fe/Mn-Ir bilayers is investigated as functions of the chemical composition of both the ferromagnetic layer and the antiferromagnetic layer. The effects of microstructure and surface modification of the antiferromagnetic layer on JK are also discussed. As a notable result, an extra large value of J$k$, which exceeds 0.5 erg/cm$^2$, is obtained for $Co_{70}Fe_{30}Mn_{75}Ir_{25}$ bilayer with the ultra-thin (50${\AA}$∼100${\AA}$) Mn-Ir layer. The exchange anisotropy of $Co_{70}Fe_{30}$ 40 ${\AA}/Mn_{75}Ir_{25}$ 100 ${\AA}$ bilayer is stable for thermal annealing up to $400{^{\circ}C}$, which is sufficiently high for the application of spin valve magnetoresistive devices.

• 한국자기학회지
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• 제14권4호
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• pp.120-126
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• 2004

DC 마그네트론 스파터링 방법으로 제작한 F $e_{84}$ N $b_{16}$ (wt.%) 박막의 온도변화에 따른 자기적 특성을 강자성 공명 흡수선의 거동을 통하여 고찰했다 모든 온도영역에서 다수의 체적 모드 스핀파와 한 개 또는 두 개의 표면 모드가 관측되었는데, 이와 같은 현상은 시편 양면의 표면 자기 이방성이 0보다 작은 경우에 나타나는 특성이다. 113-293K 온도영역에서 포화자화는 Bloch의 $T^{2}$ 3/ 법칙과 부합되는 모습을 보였으며, 분광학적 분리인자는 온도변화에 비교적 작은 변화 폭을 보였다 233-293K 온도구간에서 기판과 접하는 시편면의 표면 자기 이방성 상수 Ksl는 온도감소에 따라 그 갈이 비교적 큰 폭으로 증가하는 특성을 나타냈다. 그리고 공기와 접하는 시편면의 표면 자기 이방성 상수 $K_{sl}$ 은 상온에서 -0.322 erg/$\textrm{cm}^2$인 값을 보이다가, 온도가 253 K로 내려가면 -0.394 erg/$\textrm{cm}^2$로 감소한 후, 그 이하의 온도영역에서는 온도에 비교적 둔감한 특성을 보였다.

• 한국자기학회지
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• 제5권5호
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• pp.343-350
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• 1995

An overview will be given on recent Mossbauer and magnetization investigation of the applied field dependence of the magnetic properties of typical systems without strong magnetic anisotropy and showing the absence of magnetic saturation in high fields (including iron-rich spin glass (amorphous $Fe_{93}Zr_{7}$, soft ferromagnets (amorphous $Fe_{88}Zr_{12}$, $Fe_{70}Ni_{20}Zr_{10}$ and $Fe_{88}B_{12}$) and pure Fe). The results emphasize that shape anisotropy due to surface irregularities causes misalignment between the magnetization and the applied field in the otherwise collinear magnetic structure.

• 한국자기학회지
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• 제18권4호
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• pp.147-153
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• 2008

GaAs 기판위에 Fe을 성장시킨 이종 접합 구조는 두 물질의 lattice mismatch가 1.4 % 정도로 작기 때문에 결정 상태가 매우 좋은 Fe층을 성장시킬 수 있는 것으로 알려져있다. GaAs/Fe의 계면에서는 많은 흥미로운 현상이 관찰되며, 또한 스핀주입을 이용한 산업적 응용 면으로 가치가 있는 구조로서 활발한 연구가 진행되어 왔다. 본 연구에서는 GaAs(100) 표면에 Fe층을 쐐기모양으로 두께를 $0{\sim}3.4$ nm로 바꾸어 성장시키고 5 nm 두께의 Au층을 추가 증착시킨 시료를 Brillouin light scattering(BLS) 측정방법을 이용, 자기이방성에 대해 조사하였다. Fe층 두께를 변화시켜가며 자화 용이축과 곤란축 방향으로 외부자기장의 세기에 대한 스핀파 들뜸의 의존도와 외부자기장의 방위각에 대한 스핀파 들뜸의 의존도를 조사하였다. 측정된 결과의 정량적 분석을 통해 Fe층의 두께에 따라 일축 자기이방성 상수와 이축 자기이방성 상수를 구하였다. GaAs층 위에서 성장된 Fe층의 자기이방성은 GaAs 기판에 영향을 받아 Fe층의 두께가 얇을수록 큰 일축 자기이방성을 가지고 박막의 두께가 증가함에 따라서 Fe 본래의 이축 이방성의 크기가 증가함을 확인하였다.

• 한국자기학회지
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• 제18권3호
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• pp.98-102
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• 2008

수직자기이방성을 갖는 $[Pd/Co]_N$와 $[Pd/Co(CoFe)]_N$/FeMn 다층박막 구조를 이용하여 표면자기이방성 효과와 강자성 물질에 따른 보자력(coecivity, $H_c$)과 교환력(exchange bias, $H_{ex}$)의 변화를 관찰하였다. Ta(2.1 nm)/[Pd(3.1/N)/$Co(1.2/N)]_N$/Ta(2.1) 다층박막의 구조에서 반복층수 증가에 따라 보자력 670 Oe까지 선형적으로 증가하였으며, 교환 결합된 구조에서의 보자력은 물질에 따라 같은 증가 경향의 결과를 얻었다. 강자성 물질에 따른 가장 큰 보자력은 Co(600 Oe) > $Co_5Fe_5$(520 Oe) > $Co_8Fe_2$(320 Oe) 크기를 얻었다. 반면 교환력의 경우 반복 층수가 N=3 일 때 각 물질 모두 300 Oe의 결과 값을 얻었으며, 반복층수 3층 이후에는 $300{\sim}200$ Oe 사이에 거의 일정한 크기를 얻었다.