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MAGNETIC ANISOTROPY OF PERMALLOY THIN FILM on Mo STEPPED SURFACE

MAGNETIC ANISOTROPY OF PERMALLOY THIN FILM on Mo STEPPED SURFACE. Presented by: Ayesha Islam Roll # 09 MPhill 1st semester.

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MAGNETIC ANISOTROPY OF PERMALLOY THIN FILM on Mo STEPPED SURFACE

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  1. MAGNETIC ANISOTROPY OF PERMALLOY THIN FILM on Mo STEPPED SURFACE Presented by: Ayesha Islam Roll # 09 MPhill 1st semester

  2. What would be the effect on magnetization of permalloy thin film on Mo stepped surface grown by molecular beam epitaxy on HCP sapphire substrate, if the direction of applied magnetic field is changed. The variation of the coercivity in function of rotation angles showing that the uniaxial anisotropy axis coincides with one of the cubic anisotropy easy magnetization axis. From the magnetization curve, the effective fourfold and uniaxial anisotropy constants are determined .

  3. What would be the effect on magnetization of permalloy thin film on Mo stepped surface grown by molecular beam epitaxy on HCP sapphire substrate, if the direction of applied magnetic field is changed (Θ = 0˚,45˚,60˚,90˚,135˚,180˚).

  4. STEPPED SURFACE : Stepped surfaces can be produced by purposely miscutting a crystal forming a vicinal surface. Usually reconstruction will create a surface characterized by wide terraces separated by monoatomic steps. In some cases the steps may be 2 atomic layers high

  5. EPITAXIAL GROWTH: It’s a Greek word epi meaning «above», and taxis  meaning «in ordered manner» or «arranging upon».“ The deposited material form a crystalline overlayer that has one well-defined orientation with respect to the substrate crystal structure”

  6. MOLECULAR BEAM EPITAXY (MBE): In molecular beam epitaxy (MBE), a source material is heated to produce an  evapourated beam of particles. These particles travel through a very high vacuums (10−8 Pa) to the substrate, where they condence This technique is widely used for growing III-V semiconductor crystals

  7. HEXAGONAL CLOSED PACKED (HCP) SAPPHIRE:sapphire is gymstone of material corundum (alluminium oxide). Found naturally n used in accessories.

  8. Angle dependenceof the magnetic hysteresis loops (a plot of themagnetization in function of applied magnetic field) of aNi80Fe20/Mo(0 0 1) sample, with Ni80Fe20 layer thicknessof 100 A° and Mo layer of 100A° when Θ=0˚ direction of field is parallel to axis of step edge square loop soft magnetization remanance more coercivity

  9. Angle dependenceof the magnetic hysteresis loops (a plot of themagnetization in function of applied magnetic field) of aNi80Fe20/Mo(0 0 1) sample, with Ni80Fe20 layer thicknessof 100 A° and Mo layer of 100A° when Θ=45˚ no more square loop remanance decreases coercivity increases

  10. when Θ=60˚Rhomboid shape Hard magnetic material Remanance decreased further Coercivity increases

  11. when Θ=90˚Split loopsVery hard magnetic materialremanance is very small these results are due to the combinationof the easy character of the cubic anisotropy with thehard character of the uniaxial anisotropy .Thecompetition between surface and shape anisotropyresults in the spin reorientation from perpendicular tothe plane to parallel to the plane

  12. The characteristic split-loop hysteresis can be analytically treated as twoparts: the linear dependence in weak fields, and, twosmaller loops in the magnetic switching .The linear partin weak fields is associated with coherent spin rotationof a Stoner–Wohlfarth behavior While the potionof two smaller square loops along hysteresis could berelated with step edges

  13. when Θ=135°, 180°

  14. The variation of the coercivity in function of rotation angles showing that the uniaxial anisotropy axis coincides with one of the cubic anisotropy easy magnetization axis

  15. From the magnetization curve, the effective fourfold and uniaxial anisotropy constants can be determined following expression was used for the energy per unitvolume: ε( Θ,H)= k˳+ kʹ/4 sin² (2Θ) +k̋ sin(Θ) - Ms H sin(Θ) y = angle of the magnetization relative to the easy axis K0 = isotropic contribution, the second term corresponds to the cubic anisotropy and the third term relates to the uniaxial contribution within the film plane. Minimizing the energy w.r.t Θ

  16. Х= (2Kʹ/Ms+2k̋/Ms)ˉ1where k̋ is determined from the split field Hsplit Х Ms = k̋By taking Ms =467:9 amu /cm3 and Hsplit as an averageof shifted field in two loops, the value of k̋ = 2058:6 erg/cm3 andkʹ= 622:9 erg/cm3 is obtained for the Ni80Fe20(100A°) film deposited on stepped Mo(0 0 1).The absolute value of the cubic anisotropyconstant for bulk Ni80Fe20 is around 2103 erg/cm3.

  17. CONCLUSIONThe magnetization curves exhibit distinctive features as the magnetic field was applied either parallel or perpendicular to the step edges .For fields applied parallel to the step edges, the magnetic hysteresis shows a rectangular loop typical of the easy magnetization , when the field is applied perpendicular to the step edges, the hysteresis loopdisplays a complicated featurecomposed of two splitloops. A competing anisotropy effect of the uniaxialanisotropy at step edges with the cubic anisotropy could interpret the magnetization reversaL. In addition, from the split-loop hysteresis, the effective four-fold and uniaxial anisotropy constants are determined

  18. ana ANY QUESTION???????

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