Beenish khan Roll # 10 Ms physics (1 st semester)

1. Effect of growth temperature on the structure and magnetic properties ofsputtered biepitaxial (111) permalloy film Beenish khan Roll # 10 Ms physics (1st semester)

2. Outine line: we see… • Temperature variation on sputtered biepitaxial permalloy film • increase temperature ( coercive field decrease) • decrease temperature (coercive field increase) • no magnetocrystalline anisotropy for any biepitaxial permalloy film • uniaxial anisotropy observed in biepitaxial permaloy film

3. Some terms which are used: • Epitaxial layer : deposition of crystalline over layer on crystalline structure. • Permalloy : its a alloy of Ni and Fe (Fcc) , soft ferromagnetic alloy can easily magnetize • Sapphire : it is a single crystal of Al2O3 with hexagonal structure used as a substrate. Because has high working temperature, stable dielectric constant and good thermal conductivity

4. For analysis the film structure … EBSD : • it’s a scanning electron microscope (SEM) used to measure the crystallographic orientation • it produce image scanning it with focused beam of electron. • The electron interact with sample produce various signals. • Kikuchi band : these are bands name formed by the SEM having slightly higher and lower intensities variation. • Kikuchi bands mark orientation space with well defined intersection (called zones or poles ).

5. EBSD….and kikuchi bands

6. Introduction …multilayer film • Magnetic devices has feromagnetic (co ,FeNi) and non magnetic layers (Cu ,Ag) and then can observe the effect of exchange bias. • between these layer electrical resistance can be change due to apply field referred as GMR • in multilayer permallay / Cu film corcetivity decreases with increases total magnetic thickness • thick magnetic layer have a good soft magnetic properties

7. Experiment : Growth of biepitaxial permalloy film…. • At 750 C temperature (a subtrate sapphire temp) 250 nm thick Nb film grown by sputter deposition • At 350 c (subtrate temp) by sputtering deposition 200 cm thick Cu layer deposited on it • Then permalloy film (20 nm) deposited on Cu film by process of sputtering at 3 different subtrate temp (350 ,100 ,10) C • epitaxial layer of Cu and Py having only 1.3% mismatch.

8. Chamber pressure...and temperature : • All multilayers grown at 2.5 ^ 10 (-3) torr and chamber base pressure 1^10(-8) • deposition rate for Nb is 3A/s and for Py 4A/s. • Magnetization measure of the Py film at room temp 300k and 12 k . • All these temp and pressure Nb layer which act as a buffer layer become not a superconductor and thus not effect the magnetization • coercivity and magnetization of the Py film studied by measuring in plane magnetization [110] & [112]

9. Experimental results: EBSD Results: This technique collecting the data at different orientation of sputtered Py film and gives result at 3 different temp in the form of poles in Kikuchi bands:

10. Results at 3 different temperature

11. Epitaxial permalloy to biepitaxial permalloy film…….???? Electron move on the permalloy film and temperature of subtrate about 350 C its gives two different orientation having 2 different stacking sequence of [111] fcc plane… same for Py film and also has pattern of Cu then such layers called biepitaxial Py film and biepitaxial Cu layer

12. Stage control scanning of Py film…. • Distribution and size of biepitaxial Py film (200 nm thickness) at 350 C determined by mapping the film with the help of stage control scanning • Due to scanning the pattern , by two thick layers [111] of Py film changes widely not giving a particular pattern. • Grain size measured by linear intercept method , measured in this paper 5um

13. 200 nm thick Py film grown at subtrate temp 350 C on 20 nm epitaxial Cu film two variant shown by grey and black areas

14. Magnetization measurement

15. Hysteresis loops(variation of Hc and subtrate temp)

16. Variation of Hc with room temp and 12 K • At room temp 300 k and different subtrate temp the variation of Hc are 2.5 , 25 and 38 oe • variation in Hc at growth temp due to the production of elastic strain • variation of Hc as subtrate temp decreases due to the decrease in the crystalline quality of biepitaxial Py film

17. Graph……

18. Magnetic anisotropy

19. Magnetic and magnetocrystalline anisotropy • Magnetic properties in different direction in magnetic material knows as magnetic anisotropy • Allingment of spin in FM some specific direction imposed by crystal lattice knows as magnetocrystalline anisotropy • Epitaxial metallic film (111) plane growth direction symmetry <110> <112> 3 fold • no in plane magnetocrystalline anisotropy , so if measured in 110 or 112 has no difference as in (111)

20. Superconducting quantum interference device (magnetometer) • To study higher order aniotropies we rotate this device to study magnetization measurement from 0 to 360 degree at zero applied magnetic field • maxima and minima magnetization occur 180 degree to each other • strain induce in plane uniaxial anisotropy