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Röska, Benedikt; Park, Sohyun; Yoshimori, Yusuke; Kimura, Kenta; Kimura, Tsuyoshi (4. August 2017): Anomalous dielectric response of short hydrogen bonds under pressure. The case of (Mn,Fe)2+AlPO4(OH)2H2O. In: Journal of physics: Condensed matter, Vol. 29, No. 36, 365401
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An anomalous increase in the real part of dielectric response is observed in Mn0.5Fe0.5AlPO4(OH)2H2O while cooling to ~70 K. This is addressed to field-induced proton dynamics in a short hydrogen bond of 2.480(3) Å. The absence of discontinuities in heat capacity curves above the Néel temperature (TN ≈ 7 K) excludes a paraelectric to antiferroelectric phase transition. Upon application of mild hydrostatic pressures below 1.6 GPa, the maximum in the dielectric response is shifted from 70 K to lower temperatures near ~2 K. This explains a narrow correlation between the proton transfer and the compression of the short hydrogen bond length.