Dependence Of Ferromagnetic Resonance Field Research Articles

Determination of magnetic anisotropies and miscut angles in epitaxial thin films on vicinal (111) substrate by the ferromagnetic resonance

A method for determining magnetic anisotropy parameters of a thin single-crystal film on vicinal (111) substrate as well as substrate miscut angles from angular dependence of ferromagnetic resonance field has been proposed. The method is based on the following: (i) a new approach for the solution of the system of nonlinear equations for equilibrium and resonance conditions; (ii) a new expression of the objective function for the fitting problem. The study of the iron silicide films grown on vicinal Si(111) substrates with different miscut angles confirmed the efficiency of the method. The proposed method can be easily generalized to determine parameters of single-crystal films grown on substrates with an arbitrary cut.

NiFe 박막의 두께에 따른 강자성 공명 특성 분석

본 연구에서는 NiFe 박막 시편을 마그네트론 스퍼터링 방법으로 제조하여 박막면 기준으로 수직면(out-of-plane) 자기장 방향과 수평면(in-plane) 자기장 방향에 따른 강자성 공명 자기장을 측정하였다. 수직면 자기장 방향에 따른 강자성 공명 자기장으로부터 유효자화량(<TEX>$M_{eff}$</TEX>)을 도출하였으며, NiFe 두께에 따른 <TEX>$M_{eff}$</TEX>의 감소는 <TEX>$K_s=-0.23\;erg/cm^2$</TEX>의 값을 갖는 표면 이방성 상수에 기인하였다. 또한 수평면 자기장 방향에 따른 강자성 공명 자기장으로부터 수평면에서의 일축 이방성 자기장을 도출하였다. 한편, 일축 이방성 에너지의 자화 용이축이 두께가 감소함에 따라 시편 제조 시 인가한 자기장의 반대 방향으로 회전하고 있었으며, 이러한 현상은 시편 표면에 형성된 NiFeO의 반강자성 특성에 의한 현상으로 설명하였다. The out-of-plane and in-plane angular dependence of ferromagnetic resonance field was measured in NiFe thin films fabricated by magnetron sputtering. The effective magnetization was obtained from the out-of-plane angular dependence of ferromagnetic resonance field, which was well agreed with calculated one. The decrease of effective magnetization with NiFe thickness was due to the surface anisotropy constant of <TEX>$K_s=-0.23\;erg/cm^2$</TEX>. The in-plane uniaxial anisotropy fields were obtained from the in-plane angular dependence of ferromagnetic resonance field. The easy axis of in-plane uniaxial anisotropy field was rotated to the reverse direction of applied magnetic field during sample fabrication, which was explained by the antiferromagnetic NiFeO layer at sample surface.

Exchange Bias Induced in Polycrystalline Co/FeMn-Structures by Magnetic Field Cooling

Using the method of angular dependence of ferromagnetic resonance field the magnetic properties of Si/SiO2/Cu/Co/FeMn/Cu and Si/SiO2/Cu/Co/Cu/FeMn/Cu structures were investigated. The layer deposition was carried out by magnetron sputtering in absence of an external magnetic field. It was established that thermal annealing with further cooling down in presence of a magnetic field can generate an exchange bias at anneal temperature significantly below the bulk antiferromagnetic Néel temperature. It was also shown that a thin interlayer between ferromagnetic and antiferromagnetic layers reduces the exchange bias effect at low anneal temperatures, however, makes this effect more stable at high annealing temperatures.

Exchange Bias in Co/FeMn and Co/IrMn Structures Induced by Deposition in Presence of Magnetic Field

By measuring the angular dependence of ferromagnetic resonance field at room and low temperatures, it is demonstrated that the magnitude of magnetic field applied during magnetron deposition of Ta/F/AF/Ta structures, where F=Co, NiFe and AF=FeMn and IrMn, influences the uniaxial and unidirectional anisotropy, magnetization and the exchange bias blocking temperature. The deposition field effects on the bilayer structure are compared with the effects on a similar structure, but without antiferromagnetic layer. The exchange bias blocking temperature of investigated structures is found to be significantly lower than the Néel temperature of a bulk antiferromagnet. The origin of the observed effects is shortly discussed.

Ferromagnetic resonance studies of Fe thin films with dilute heavy rare-earth impurities

The structure and magnetic properties of Fe1−xGd(Tb)x films prepared by sputtering have been investigated using x-ray diffraction, vibrating sample magnetometer, and ferromagnetic resonance. Magnetic measurements show that the saturation magnetization decreases as the increase of Gd(Tb) content, which agrees with that Gd(Tb) atomic moments align antiparallel with Fe moments. Theoretical fittings of the angular dependence of ferromagnetic resonance field yield the second- and forth-order perpendicular anisotropy constants K⊥1 and K⊥2, which show a spin reorientation with increasing Gd(Tb) doping. The intrinsic contribution of ferromagnetic resonance linewidth as a result of Gilbert damping is separated from the extrinsic contribution because of the inhomogeneity of the films. It is found that the additions of Gd additives do not significantly improve the damping constant, whereas the Tb dopants increase the damping constant from 0.04 without Tb to 0.11 with 19% Tb, thus a remarkable enhancement of 175%.

The dependence of magnetic properties of Co/FeMn bilayer structure on the magnitude of magnetic field applied during the layer deposition

By measuring the angular dependence of ferromagnetic resonance field at room and low temperatures, it is demonstrated that the magnitude of magnetic field applied during magnetron deposition of Ta/Co/FeMn/Ta structures influences their magnetic properties such as uniaxial and unidirectional anisotropy, magnetization and the exchange bias blocking temperature. The deposition field effects on the bilayer structure are compared with the effects on a similar structure, but without antiferromagnetic layer. The exchange bias blocking temperature of investigated structures is found to be significantly lower than the Néel temperature of a bulk antiferromagnet. The origin of the observed effects is shortly discussed.

Temperature dependence of exchange bias in Co/FeMn-structure induced by heating and cooling in magnetic field

Using the method of angular dependence of ferromagnetic resonance field the magnetic properties of Si/SiO2/Cu/Co/FeMn/Cu and Si/SiO2/Cu/Co/Cu/FeMn/Cu structures were investigated. The layer deposition was carried out by magnetron sputtering in absence of an external magnetic field. It was established that thermal annealing with further cooling down in presence of a magnetic field can generate an exchange bias at anneal temperature significantly below the bulk antiferromagnetic Néel temperature. It was also shown that a thin interlayer between ferromagnetic and antiferromagnetic layers reduces the exchange bias effect at low anneal temperatures, however, makes this effect more stable at high annealing temperatures.