- #1
gony rosenman
- 11
- 4
Member advised to use the formatting template for all homework help requests
hello i have a few questions regarding hysteresis loop in ferromagnets as showen here .
i had an experiment in which i took a piece of gadolinium and cooled it down using liquid nitrogen , than i put it in an apparatus as showen here , so i induct an oscillating magnetic field on it , forcing some inner magnetization to arise within the metal , according to blochs law .
M(T) = M(0)*(1-(T/Tcurie)3/2)
M(T) - inner magnetization
M(0) - inner magnetization at absolute zero
T - Temperature
Tcurie - curie temperature , in which the magnetic domains cannot form a unified direction and the metal become paramagnetic
now things get tricky for me
i learned that in hysteresis loops , the inner magnetization is measured as the magnitude of B at the retentivity point (which makes sense cause that's the field that remain in the metal when there is no magnetic field induced) , but that is confusing because that value is in units of Tesla/Gauss , and i wanted to find the Magnetization in amper/meter units .
am i getting something wrong , or should i just convert to amper/meter , and if so - which formula should i use ?
further more , in the experiment i measure the voltage drop on the capacitor C2 (shown in figure) and get a signal proportional to B , with an unknown factor which i am unable to attain from the lab ( apparently no one knows the precise inductance of the coil , i measured it by myself but decided i rather keep the whole data with volatages and show proportionality) , so in the end the value extracted from the hysteresis loop was only proportional to B at the retentivity point .
nevertheless , i decided to fit the data using CFtool (matlab) and a costume equation similar to bloch's law (meaning i took the value of V proportional to B at the retentivity point of each hysteresis loop corresponding to a different Temperature , and plot it against the matching temperature , and tried to make a fit with bloch's law equation)
the striking part , the results were surprisingly close to the expected values . for example , i looked up the inner magnetization and saw the following for gadolinium :
The saturation magnetization at absolute zero, determined by extrapolation is 253.6±0.9 cgs units .
This saturation moment corresponds to 7.12 Bohr magnetons.
the value i got in the CFtool for M(0) was around 700 , which is in the same order of magnitude . so my final question , is it a coincidence or does it make sense somehow that my proportional measurment somehow corresponds well to the actual value , and that my measurement was in units of B when maybe it should have been somehow converted to units of magnetization .that is a very long question , i hope someone out there might be able to assist with some clarification , there's not much i can do in return but send honest gratitude !
i had an experiment in which i took a piece of gadolinium and cooled it down using liquid nitrogen , than i put it in an apparatus as showen here , so i induct an oscillating magnetic field on it , forcing some inner magnetization to arise within the metal , according to blochs law .
M(T) = M(0)*(1-(T/Tcurie)3/2)
M(T) - inner magnetization
M(0) - inner magnetization at absolute zero
T - Temperature
Tcurie - curie temperature , in which the magnetic domains cannot form a unified direction and the metal become paramagnetic
now things get tricky for me
i learned that in hysteresis loops , the inner magnetization is measured as the magnitude of B at the retentivity point (which makes sense cause that's the field that remain in the metal when there is no magnetic field induced) , but that is confusing because that value is in units of Tesla/Gauss , and i wanted to find the Magnetization in amper/meter units .
am i getting something wrong , or should i just convert to amper/meter , and if so - which formula should i use ?
further more , in the experiment i measure the voltage drop on the capacitor C2 (shown in figure) and get a signal proportional to B , with an unknown factor which i am unable to attain from the lab ( apparently no one knows the precise inductance of the coil , i measured it by myself but decided i rather keep the whole data with volatages and show proportionality) , so in the end the value extracted from the hysteresis loop was only proportional to B at the retentivity point .
nevertheless , i decided to fit the data using CFtool (matlab) and a costume equation similar to bloch's law (meaning i took the value of V proportional to B at the retentivity point of each hysteresis loop corresponding to a different Temperature , and plot it against the matching temperature , and tried to make a fit with bloch's law equation)
the striking part , the results were surprisingly close to the expected values . for example , i looked up the inner magnetization and saw the following for gadolinium :
The saturation magnetization at absolute zero, determined by extrapolation is 253.6±0.9 cgs units .
This saturation moment corresponds to 7.12 Bohr magnetons.
the value i got in the CFtool for M(0) was around 700 , which is in the same order of magnitude . so my final question , is it a coincidence or does it make sense somehow that my proportional measurment somehow corresponds well to the actual value , and that my measurement was in units of B when maybe it should have been somehow converted to units of magnetization .that is a very long question , i hope someone out there might be able to assist with some clarification , there's not much i can do in return but send honest gratitude !