Pgfplots Globale Achsenbeschriftung, Titel, Legende für zwei Diagramme erstellen

\documentclass[chapterprefix=true, 12pt, a4paper, oneside, parskip=half, listof=totoc, bibliography=totoc, numbers=noendperiod]{scrbook}
    \usepackage{pgfplots}
    \pgfplotsset{compat=newest}
    \usepgfplotslibrary{groupplots}
    \usepackage{tikz}
    \begin{document}
    \begin{figure}[ht]
    \caption*{Grathöhe $h_{0}$}
    \begin{tikzpicture}
      \begin{semilogxaxis}[width=7.9cm,height=7.9cm,ylabel shift = -0.3cm,
        xlabel={ $a_{e}$ in mm},
        ylabel={$h_{0}$ in $\mu$m},
        xmin=0, xmax=1.0,
        ymin=0, ymax=1000,
        xtick={0,0.02,0.05,0.1,0.2,0.5,1.0},
        ytick={0,250,500,750,1000},
        log ticks with fixed point,
        %legend style={at={(0.5,-0.1)},anchor=north},
        %ymajorgrids=false,
        %xmajorgrids=false,
        %grid style=dashed,
        /pgf/number format/.cd,
        use comma,
        1000 sep={},
        legend columns=-1,
        legend entries={Sonstiges, Nichts},
        legend style={at={(0.5,-0.1)},anchor=north},
        legend to name=named
        ]
        \addplot [mark=diamond*,red]  coordinates {
            (0.02,68)
            (0.05,416)
            (0.2,441)
            (0.5,309)
            (1.0,351)
          };
          %node [small dot,pin=120:{$\gamma=90^\circ$}]      at (axis description cs:0,1)      {};
          \addplot [mark=square*,blue] coordinates {  
            (0.02,119)
            (0.05,389)
            (0.1,408)
            (0.2,359)
            (0.5,268)
            (1.0,283)
          };
          \node at (axis cs:0.03,900){$\gamma=90^\circ$};
        \end{semilogxaxis}
      \end{tikzpicture}
      \begin{tikzpicture}
      \begin{semilogxaxis}[width=7.9cm,height=7.9cm,ylabel shift = -0.3cm,
      xlabel={ $a_{e}$ in mm},
        ylabel={ $h_{0}$ in $\mu$m},
        xmin=0, xmax=1.0,
        ymin=0, ymax=1000,
        xtick={0,0.02,0.05,0.1,0.2,0.5,1.0},
        ytick={0,250,500,750,1000},
        log ticks with fixed point,
        %legend style={at={(0.5,-0.1)},anchor=north},
        %ymajorgrids=false,
       % xmajorgrids=false,
       % grid style=dashed,
        /pgf/number format/.cd,
        use comma,
        1000 sep={},
        ]
        \addplot [mark=diamond*,red] coordinates {  
            (0.02,389)
            (0.05,672)
            (0.2,829)
            (0.5,360)
            (1.0,776)
          };
    %node [small dot,pin=120:{$\gamma=60^\circ$}]      at (axis description cs:1,1)      {};
          \addplot [mark=square*,blue]  coordinates {
            (0.02,252)
            (0.05,239)
            (0.1,322)
            (0.2,519)
            (0.5,433)
            (1.0,479)
          };
            \node at (axis cs:0.03,900){$\gamma=60^\circ$};
        \end{semilogxaxis}
    \end{tikzpicture}
    \begin{center}
    \ref{named}
    \label{dia1}
    \caption{Bildunterschrift}
    \end{center}
    \end{figure}
    \end{document}