Stoner.analysis.fitting.models.superconductivity.ic_B_airy(B, Ic0, B_offset, A)[source]

Calculate Critical Current for a round Josepshon Junction wrt to Field.

  • B (array-like) – Magnetic Field (structly flux density in T)

  • Ic0 (float) – Maximum critical current

  • B_offset (float) – Field offset/trapped flux in coils/remanent M in junction

  • A (fl,oat) – Area of junction in $m^2$


(array) – Values of critical current


Represents the critical current as:
:math:`I_{c0}timesleft|frac{2 J_1left(frac{pi(B-B_{offset}) A}right)}{Phi_0}}

{frac{pi(B-B_{offset}) A}){Phi_0}}right|`

where \(J_1\) is a first order Bessel function.

For small ($<1^{-5}$)values of the Bessel function argument, this will return Ic0 to ensure correct evaluation for 0 flux.


#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Fit Ic(B) to Airy function."""
import os

from Stoner import Data, __home__
from Stoner.analysis.fitting.models.superconductivity import Ic_B_Airy

os.chdir(os.path.join(__home__, "..", "doc", "samples", "Fitting"))

data = Data("data/Ic_B.txt", setas={"x": "Magnet Output", "y": "Ic"})

data.lmfit(Ic_B_Airy, result=True, header="Fit")

data.setas = {"x": "Magnet Output", "y": ["Ic", "Fit"]}
data.plot(fmt=["r+", "b-"])

data.annotate_fit(Ic_B_Airy, mode="eng", x=0.6, y=0.5, fontsize="small")

data.title = "Critical current vs Field for $4\mu m$ junction"
data.xlabel = r"Magnetic Field $\mu_0H (\mathrm{T})$"
data.ylabel = r"Critical Current $I_c (A)$"

(png, hires.png, pdf)