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Alisha Vira edited subsection_Varying_the_Polarization_Time__.tex
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\subsection{Varying the Polarization Time}
We first measured the Larmor frequency, as described in the Methods, and found a value of $1.852\pm0.018~kHz$, which is very close as the manual says that the precession frequency should be approximately 2 kHz. We expect magnetization, and therefore voltage, to change exponentially with changing polarization time according to Equation~\ref{eq:growthrate} \cite{TeachSpin}. By plotting data for three different times after the polarization field was no longer applied, as shown in Fig.~\ref{fig:measurepolarizationtime} and discussed in the Methods, we could fit the data to
Equation~\ref{eq:growthrate} Eq.~\ref{eq:growthrate} and obtain values for the spin-lattice relaxation time ${T_1}$, which should be the same for our three different curves. We found ${T_1}=2.15\pm0.05 s$.
\subsection{Varying the Current}
We also varied current, keeping all other values constant, and measured precession frequency. We found there to be no dependence, as expected and predicted by
Equation~\ref{eq:precession}. Eq.~\ref{eq:precession}. We expect the magnetization to vary according to
Equation~\ref{eq:tanh} Eq.~\ref{eq:tanh} when we artificially increase Earth's magnetic field, using a constant polarization time (which was in this case 10 seconds), as seen in Fig.~\ref{fig:polarizationtime10s}. Our data was initially plotted against voltage, not magnetization, but Eq.~\ref{eq:tanh} allows us to find magnetization as we can calculate $\mu$ using
\begin{equation}
\label{eq:mu}
\mu=\gamma\hbar\sqrt{I(I+1)}