Insert a separate mark inside a pgfplots graph

Question

First of all, let me apologize if the title is not enough clear, but I didn't know how to explain myself better.

I have a graph consisting in three different curves that are covering almost the same y range, except for one point. Since this point corresponds to a value of y much higher respect to the others, I don't want to report it directly, because it would cause the flattening of all the other points. My solution is therefore to report this only point in a separate position of my graph, with an arrow that indicates that it is out of the range and its coordinates:

\documentclass{scrbook}
\usepackage{classicthesis}
\usepackage{tikz}
\usepackage{pgfplots}
\begin{document}

\begin{tikzpicture}
    \begin{axis}[
     xlabel={x},
     ylabel={y},
     xmin=0, xmax=120,
     ymin=0, ymax=5,
     width=.8\columnwidth,
     cycle list name=black white,
     /pgfplots/ytick={1,2,...,5}]
     \addplot
     coordinates{
     (3,    25)
     (5,    4)
     (10,   2)
     (20,   1)
     (40,   0.5)
     };
     \addplot
     coordinates{
     (6,    4)
     (10,   2)
     (20,   1)
     (40,   0.5)
     (80,   0.5)
     };
     \addplot
     coordinates{
     (9,    3)
     (15,   1.5)
     (30,   0.5)
     (60,   0.5)
     (120,  0.5)
     };
     \node at (axis cs:25,4.5) {$\uparrow(3,25)$};
     \legend{1,2,3}
     \end{axis}
\end{tikzpicture}

\end{document}

Here is what I'm asking you:

• As you can notice, I'm using the \uparrow symbol to create the arrow, but I would like a thinner and longer arrow.
• I would like not to be obliged to report the coordinates of the point by hand.
• I would like to add a mark between the arrow and the coordinates, which should have the same style of the first curve.

Thanks for your help.

EDIT:

Although I'm not completely satisfied about it, I adopted the following solution:

\documentclass{scrbook}
\usepackage{classicthesis}
\usepackage{tikz}
\usepackage{pgfplots}
\begin{document}

\begin{tikzpicture}
    \begin{axis}[
     xlabel={x},
     ylabel={y},
     xmin=0, xmax=120,
     ymin=0, ymax=5,
     width=.8\columnwidth,
     cycle list name=black white,
     /pgfplots/ytick={1,2,...,5}]
     \addplot
     coordinates{
     (3,    25)
     (5,    4)
     (10,   2)
     (20,   1)
     (40,   0.5)
     };
     \addplot
     coordinates{
     (6,    4)
     (10,   2)
     (20,   1)
     (40,   0.5)
     (80,   0.5)
     };
     \addplot
     coordinates{
     (9,    3)
     (15,   1.5)
     (30,   0.5)
     (60,   0.5)
     (120,  0.5)
     };
     \draw[-latex] (axis cs:12,4.25) -- (axis cs:12,4.75);
     \addplot[fill=gray,mark=*]
     coordinates{
     (15.5, 4.5)
     };
     \node[right] at (axis cs:16,4.5) {$(3,25)$};
     \legend{1,2,3}
     \end{axis}
\end{tikzpicture}

\end{document}

Here is the result:

Answer 1

An alternative approach could be to use the key restrict y to domain*=0:5.5, which will limit the maximum y value to 5.5, in conjunction with clip=false, which allows plots to extend past the plot boundary. You could then place a label node and a positioning node which can be used for drawing a "break" symbol:

\documentclass{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\begin{document}

\begin{tikzpicture}
    \begin{axis}[
     xlabel={x},
     ylabel={y},
     xmin=0, xmax=120,
     ymin=0, ymax=5,
     width=.8\columnwidth,
     cycle list name=black white,
     /pgfplots/ytick={1,2,...,5},
     clip=false,
     restrict y to domain*=0:5.5]
     \addplot
     coordinates{
     (3,    25)
     (5,    4)
     (10,   2)
     (20,   1)
     (40,   0.5)
     } node [pos=0,anchor=west] {(3\,,\,25)}
        node (break) [pos=0.0125,inner sep=0pt,minimum width=0.75em, minimum height=0.5ex,fill=white] {};
     \draw [fill=red] (break.north east) -- (break.north west) (break.south west) -- (break.south east);
     \addplot
     coordinates{
     (6,    4)
     (10,   2)
     (20,   1)
     (40,   0.5)
     (80,   0.5)
     };
     \addplot
     coordinates{
     (9,    3)
     (15,   1.5)
     (30,   0.5)
     (60,   0.5)
     (120,  0.5)
     };
     \legend{1,2,3}
     \end{axis}
\end{tikzpicture}

\end{document}

Answer 2

You could use the resizebox command provided by th graphicx package:

\documentclass{scrbook}
\usepackage{classicthesis}
\usepackage{tikz}
\usepackage{pgfplots}

\usepackage{graphicx}
\usetikzlibrary{arrows}

\begin{document}

\begin{tikzpicture}
    \begin{axis}[
     xlabel={x},
     ylabel={y},
     xmin=0, xmax=120,
     ymin=0, ymax=5,
     width=.8\columnwidth,
     cycle list name=black white,
     /pgfplots/ytick={1,2,...,5}]
     \addplot
     coordinates{
     (3,    25)
     (5,    4)
     (10,   2)
     (20,   1)
     (40,   0.5)
     };
     \addplot
     coordinates{
     (6,    4)
     (10,   2)
     (20,   1)
     (40,   0.5)
     (80,   0.5)
     };
     \addplot
     coordinates{
     (9,    3)
     (15,   1.5)
     (30,   0.5)
     (60,   0.5)
     (120,  0.5)
     };
     %  \node at (axis cs:25,4.5) {$\uparrow(3,25)$};
     \node at (axis cs:25,4) {\resizebox{2mm}{10mm}{$\uparrow$}(3,25)};
     %\draw[-latex] (axis cs:25,3.7) -- node[right] {(3,25)} (axis cs:25,4.7) ;
     \legend{1,2,3}
     \end{axis}
\end{tikzpicture}

\end{document}

Alternatively, you could also use TikZ to draw the arrow, where you can choose from different arrow tips if you load the arrows library (see this quick reference) via

\draw[-latex] (axis cs:25,3.7) -- node[right] {(3,25)} (axis cs:25,4.7);