Sublattice‐Resolved Magnetoelastic Coupling and Opposing Pressure Responses in the Frustrated Magnetocaloric GdMn 2 O 5

Frustrated multiferroic manganites exhibit strong lattice‐charge‐magnetic coupling, enabling complex phase transitions and tunable magnetocaloric responses for cryogenic cooling. Here, we systematically investigate GdMn 2 O 5 to elucidate its structure, magnetic ordering, magnetocaloric properties, and pressure response. Structural studies reveal an orthorhombic Pbam framework with no global phase transition from 4–300 K, but instead show anisotropic thermal expansion, including negative expansion along the b ‐axis, driven by magnetoelastic coupling. Microscopy and X‐ray absorption spectroscopy confirm Mn 3+ /Mn 4+ charge ordering between octahedral and pyramidal sites, with an effective coordination number of 5.5. The compliant Mn–Gd interface acts as the primary transducer of magnetoelasticity, exhibiting anomalous spin‐phonon coupling. Magnetic measurements reveal successive transitions: T N ≈ 39 K (Mn 3+ /Mn 4+ antiferromagnetic ordering), T SR ≈ 34 K (spin‐reorientation), and T Gd ≈ 3.5 K (Gd 3+ ordering). Under 0–7 T, the material displays a conventional magnetocaloric effect with a maximum entropy change of 16.1 J/kg K at ∼8 K and a relative cooling power of 272 J/kg, surpassing prior reports. Hydrostatic pressure reveals opposing responses: T N decreases, consistent with weakened Mn–O–Mn exchange, while T Gd increases, suggesting enhanced Mn–Gd coupling under compression. These results highlight GdMn 2 O 5 as a promising cryogenic magnetocaloric material and reveal a sublattice‐dependent pressure‐tuning mechanism relevant to frustrated multiferroics.