Evolution of spin freezing transition and structural, magnetic phase diagram of Dy[Formula: see text]La[Formula: see text]Zr[Formula: see text]O[Formula: see text] (0 [Formula: see text] [Formula: see text] [Formula: see text] 2.0)

Muon spin relaxation and emergence of disorder-induced unconventional dynamic magnetic fluctuations in Dy2Zr2O7

The disordered pyrochlore oxide Dy2Zr2O7shows the signatures of field-induced spin freezing with remnant zero-point spin-ice entropy at 5 kOe magnetic field. We have performed zero-field and longitudinal field Muon spin relaxation (µSR) studies on Dy2Zr2O7. Our zero field studies reveal the absence of both long-range ordering and spin freezing down to 62 mK. TheµSR relaxation rate exhibits a temperature-independent plateau below 4 K, indicating a dynamic ground state of fluctuating spins similar to the well-known spin ice system Dy2Ti2O7. The low-temperature spin fluctuations persist in the longitudinal field of 20 kOe as well and show unusual field dependence of the relaxation rate, which is uncommon for a spin-liquid system. Our results, combined with the previous studies do not show any evidence of spin ice or spin glass ground state, rather point to a disorder-induced dynamic magnetic ground state in the Dy2Zr2O7material.

Field induced spin freezing and low temperature heat capacity of disordered pyrochlore oxide Ho2Zr2O7

Spin ice materials are the model systems that have a zero-point entropy as T ! 0 K, owing to the frozen disordered states. Here, we chemically alter the well-known spin ice Ho2Ti2O7 by replacing Ti sites with isovalent but larger Zr ion. Unlike the Ho2Ti2O7 which is a pyrochlore material, Ho2Zr2O7 crystallizes in disordered pyrochlore structure. We have performed detailed structural, ac magnetic susceptibility and heat capacity studies on Ho2Zr2O7 to investigate the interplay of structural disorder and frustrated interactions. The zero-field ground state exhibits large magnetic susceptibility and remains dynamic down to 300 mK without showing Pauling's residual entropy. The dynamic state is suppressed continuously with the magnetic field and freezing transition evolves ( 10 K) at a field of 10 kOe. These results suggest that the alteration of chemical order and local strain in Ho2Ti2O7 prevents the development of spin ice state and provides a new material to study the geometrical frustration based on the structure.