I need overlay or nest a figure in a graph. I try with \pic, but the results aren't good for figure scale, according to graph scale.
I try also to define the figure in nodes, to place it in the graph, but I can't.
\documentclass[11pt]{report}
\usepackage[T1]{fontenc}
\usepackage{titlesec}
\usepackage{calc}
\usepackage{lmodern}
\usepackage{lipsum}
\usepackage{graphicx}
\usepackage{tikz}
\usepackage{pgfplots}
\begin{document}
\tikzset{m2/.pic={
\draw (0,0)--(0,.4)--(1.575,.4)--(1.575,7.8)--(0,7.8)--(0,8.2)--(3.4,8.2)--(3.4,7.8)--(1.825,7.8)--(1.825,.4)--(3.4,.4)--(3.4,0)--cycle;
}}
\begin{figure}[!hbp]
\centering
\begin{minipage}[c]{0.4\linewidth}
\centering
\begin{tikzpicture}
\begin{axis}[ymin=0,xmin=-4000,x=.0035mm,y=1cm, axis x line=bottom,axis y line=left,clip=false]
\addplot[mark=none,red,very thick] coordinates{(406,8)(406,7)(823,7)(823,6)(1131,6)(1131,5)(1384,5)(1384,4)(1581,4)(1581,3)(1751,3)(1751,2)(1856,2)(1856,1)(1913,1)(1913,0)};
\addplot[mark=none,red,very thick] coordinates{(-406,8)(-406,7)(-823,7)(-823,6)(-1131,6)(-1131,5)(-1384,5)(-1384,4)(-1581,4)(-1581,3)(-1751,3)(-1751,2)(-1856,2)(-1856,1)(-1913,1)(-1913,0)};
\addplot[mark=none] coordinates{(0,0)(0,8)};
\end{axis}
\end{tikzpicture}
\end{minipage}%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{minipage}[c]{0.4\linewidth}
\centering
\begin{tikzpicture}
\begin{axis}[ymin=0,xmax=5000,x=.0035mm,y=1cm, axis x line=bottom,hide y axis,clip=false]
\addplot[mark=none,red,very thick] coordinates{(822,8)(822,7)(1444,7)(1444,6)(1898,6)(1898,5)(2268,5)(2268,4)(2560,4)(2560,3)(2735,3)(2735,2)(2859,2)(2859,1)(2610,1)(2610,0)};
\addplot[mark=none,red,very thick] coordinates{(-822,8)(-822,7)(-1444,7)(-1444,6)(-1898,6)(-1898,5)(-2268,5)(-2268,4)(-2560,4)(-2560,3)(-2735,3)(-2735,2)(-2859,2)(-2859,1)(-2610,1)(-2610,0)};
\node at (axis cs: 2610,0.5) [font=\scriptsize, right] {$\sigma 2$};
\addplot[mark=none] coordinates{(0,0)(0,8)};
\pic [scale=50] at (500,400) {m2};
\end{axis}
\end{tikzpicture}
\end{minipage}
\end{figure}
\end{document}


