I have recently performed Ferromagnetic measurements of doped BTO thin films. (see attached).
My sample shows Ferromagnetic behaviors between the ranges of +-1.5KOe(red), with the substrates diamagnetic response dominating beyond this range. I attempted to compensate for this effect (blue) however, due to slight variations in the geometry of sample B and the reference sample, this was not accurate enough to show saturation in the ferroelectric loop.
The bulk sample has recorded remnant magnetisation of 7.8memu/g(ref). So for my thin film with a mass of 3.77x10^-5g (mass = density x volume, 9.03g/cm^3 x 4.176x10^-6cm^3), the total remnant magnetization should stand at 2.94x10^-7emu. Looking at the zoom in, you can see that this is within the range of the samples, However the influence of noise and diamagnetic substrate influence dominate any accurate Ferromagnetic reading.
While I believe there is evidence of ferromagnetism my sample, If it is to be accurately measured, the thin film contribution must be increased to determine it from noise and substrate influence. My films are currently 400nm thick, but I intend to try 800nm, 2000nm and 4000nm thicknesses in order to increase the magnetic moment. Would anyone advise me in the course of action, or recommend any other approach?
http://scitation.aip.org/content/aip/journal/apl/95/8/10.1063/1.3213344
A possible effect in your sample is the break in total magnetic ordering. In the bulk arrangement the tendency are the magnetic moments were opposite; whereas, in thin films only one surface is exposed because the other surface is bonding, increasing the total magnetic moment.
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