Muon spin relaxation ($\mu$SR) [#!SternliebJMMM92!#,#!UemuraHI94!#]

As introduced in Chapter 1, $\mu$SR is sensitive to dilute and/or small static moments. In the measurements of NENP, there were no static fields observed down to 20 mK, supporting the non-magnetic ground state [94]. Similar measurements have been performed on other Haldane materials, such as AgVP₂S₆ [95], TMNIN [96] and NINO [96], and none of these measurements have detected any static order down to the milli-Kelvin regime.