Magnetic moment

The definition of magnetic momentum, as well as orbital and spin magnetic moment.
Also see the muon anomalous magnetic moment g-2.

The force on a loop of current due to a magnet:

Magnetic moment of a solenoid with current:

Orbital magnetic moment:

Magnetic moment of an electron:

Magnetic moment and spin of an electron:

Magnetic moment and spin of a positron:

Spin flip:

Edit and compile if you like:

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% Author: Izaak Neutelings (March 2020)
\documentclass[border=3pt,tikz]{standalone}
\usepackage{amsmath} % for \dfrac
\usepackage{bm} % \bm
\usepackage{physics}
\usepackage{tikz,pgfplots}
\usepackage[outline]{contour} % glow around text
\usetikzlibrary{angles,quotes} % for pic (angle labels)
\usetikzlibrary{calc}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{patterns,snakes}
\tikzset{>=latex} % for LaTeX arrow head
\contourlength{1.6pt}
\usepackage{xcolor}
\colorlet{Bcol}{violet!90}
\colorlet{BFcol}{red!60!black}
\colorlet{Scol}{green!60!black}
\colorlet{veccol}{green!45!black}
\colorlet{Icol}{blue!70!black}
\colorlet{mucol}{red!90!black}
\tikzstyle{BField}=[->,thick,Bcol]
\tikzstyle{current}=[->,Icol] %thick,
\tikzstyle{force}=[->,thick,BFcol]
\tikzstyle{vector}=[->,thick,veccol]
\tikzstyle{mu vector}=[->,thick,mucol]
\tikzstyle{spin}=[->,very thick,Scol]
\tikzstyle{velocity}=[->,very thick,vcol]
\tikzstyle{charge+}=[very thin,draw=black,top color=red!50,bottom color=red!90!black,shading angle=20,circle,inner sep=0.5]
\tikzstyle{charge-}=[very thin,draw=black,top color=blue!50,bottom color=blue!80,shading angle=20,circle,inner sep=0.5]
\tikzstyle{metal}=[top color=black!15,bottom color=black!25,middle color=black!5,shading angle=10]
\tikzset{
  BFieldLine/.style={thick,Bcol,decoration={markings,mark=at position #1 with {\arrow{latex}}},
                                 postaction={decorate}},
  BFieldLine/.default=0.5,
  pics/magnet/.style={ %args={#1}
    code={
      \def\h{0.9}
      \coordinate (-N) at (0,\h);
      \coordinate (-S) at (0,-\h);
      \draw[pic actions,thick,top color=red!60,bottom color=red!90,shading angle=20]
        (-0.8*\h/2,0) rectangle ++(0.8*\h,\h);
 
 
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