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 Hikami Larkin Nagaoka (HLN) formula fitting		  New Topic  Reply to Topic
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Thanassis

Greece
1 Posts
Posted - 01/23/2018 :  03:53:42 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
I have been using the HLN equation to fit magnetoconductivity at low temperatures but haven't been able to make a good fit till now. I thought I might take the help on this forum to succeed in it.
Looking forward to your suggestions,

Thanks

Shirley_GZ

China
Posts
Posted - 01/23/2018 :  04:40:59 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

As I know, Origin doesn't have such built-in equation. So, you defined this fitting function by yourself, right?

Could you send us the FDF file and Origin project file with the fitting results via tech@originlab.com? Also the detailed equation you are following to define the fitting function?

Thanks,
Shirley

Originlab Technical Service Team
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Alex31

Greece
1 Posts
Posted - 02/07/2018 :  09:10:52 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
The Hikami-Larkin-Nagaoka formula is of the form:
Y=a{Ψ(1/2+b/X)-ln(b/X)},
where a,b are fitting parameters and the function Ψ(1/2+b/X) is the digamma function which is defined as the logarithmic first derivative of the gamma function.
Ψ(Χ)=d/dX(lnΓ(Χ))
The problem is that origin does not have the digamma function so that we can use it to built the equation. Is there any way we overcome this problem?

Thank you in advance!
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Shirley_GZ

China
Posts
Posted - 02/08/2018 :  04:45:10 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Alex,

Origin has a LabTalk function Real_polygamma and an Origin C function real_polygamma which are variants of the digamma function.
https://www.originlab.com/doc/LabTalk/ref/Real-polygamma-func
https://www.originlab.com/doc/OriginC/ref/real_polygamma

With these two functions, you need set k=0, and then use them to define your HLN function. About how to define fitting functions by yourself, please refer to
https://www.originlab.com/index.aspx?go=support/videotutorials&pid=1172
https://www.originlab.com/doc/Tutorials/UserDef-FitFunc

Thanks,
Shirley



Originlab Technical Service Team
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