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Structural analysis of spin frustrated Ho 2 Ge x Ti 2−x O 7 (x = 0, 0.1, 0.15 & 0.25) pyrochlore oxides has been performed using high resolution x-ray diffraction pattern and low temperature synchrotron x-ray diffraction pattern. The effect of positive chemical pressure on the spin dynamics of Ho 2 Ge x Ti 2−x O 7 has been analysed through the study of static (M-T and M-H; magnetisation against temperature & magnetisation against magnetic field) and dynamical (ac susceptibility) magnetic measurements. In lower temperature regime (∼2 K), such systems are predominantly governed by competing exchange (J nn ) and dipolar (D nn ) magnetic interactions. Magnetic measurements indicate that the application of increased chemical pressure in Ho 2 Ti 2 O 7 matrix propels the system towards diminished ferromagnetic interaction. Dipolar coupling constant remains almost unchanged but Curie-Weiss temperature (θ cw ) reduces to −0.04 K from 0.33 K (for an applied magnetic field; H = 100 Oe) with increasing x in Ho 2 Ge x Ti 2−x O 7 . Positive chemical pressure establishes the dominance of Ho-Ho antiferromagnetic interaction J nn over dipolar interaction D nn . Spin relaxation feature corresponding to thermally activated single ion freezing (T s ∼ 15 K) is shifted towards lower temperature. This chemical pressure-driven T s shift is ascribed to the alteration in crystal field effect, which reduces the activation energy for singe ion spin freezing. The reduction in the activation energy indicates crystal field-phonon coupling in Ho 2 Ge x Ti 2−x O 7 system. The robustness in spin ice freezing (second spin relaxation feature in ac susceptibility curve) remains unaffected with increasingly chemical pressure. This spin freezing ('2 in-2 out' spin arrangement in tetrahedra) is related to quantum tunnelling phenomenon, at T ice ∼ 2 K. It indicates that majority of spins still follows the 'ice rule' in Ho 2 Ge x Ti 2−x O 7 even after the application of chemical pressure.

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