We present a comprehensive study of the magnetic structure evolution, employing bulk magnetization and neutron powder diffraction (NPD) measurements down to 3.5 K, across the spin reorientation transition in orthorhombic (Pnma) ${\mathrm{TmCrO}}_3$. Magnetic susceptibility reveals canted antiferromagnetic (CAFM) ordering at $T_N=125\mathrm{K}$, followed by the magnetization reversal, showing minima between the two compensation points $T_{\mathrm{comp}1}$ and $T_{\mathrm{comp}2}$. Heat capacity shows a λ-transition at $T_N$, associated with long-range antiferromagnetic order of Cr, followed by a broad feature at ∼ 9 K, arising due to Schottky-type anomaly. Magnetic refinement of NPD data establishes the $P{n}^{\prime }{m}^{\prime }a$: Γ2($C_x,G_y;C_x^{Tm},F_z^{Tm}$) CAFM structure below $T_N$. A gradual change in magnetic structure occurs during the spin-reorientation (SRO) transition below 30 K. During this, the magnetic structure gradually changes from $P{n}^{\prime }{m}^{\prime }a$ (Γ2) to $P{n}^{\prime }m{a}^{\prime }$ (Γ4): $A_x,F_y,G_z;F_y^{Tm}$. Below 30 K, however, neither Γ2 nor Γ4 alone adequately fit the intensity of magnetic reflections. A satisfactory refinement could only be achieved in the monoclinic subgroup $P{2^{\prime }}_1/c^{\prime }$ derived from a combination of Γ2 and Γ4. The observed gradual SRO of Tm and Cr moments is consistent with the magnetic symmetry $P{2^{\prime }}_1/c^{\prime }$: $C_x,G_y,G_z;C_x^{Tm},F_y^{Tm},F_z^{Tm}$. Furthermore, the ordered moments Cr and Tm in ${\mathrm{TmCrO}}_3$ exhibit a complex, nonmonotonic temperature dependence as expected during SRO. Anomalies in lattice parameters suggest magnetoelastic coupling, linking structural distortions to the SRO.

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• Spin reorientation transition
• Antiferromagnets
• Rare-earth magnetic materials
• Neutron diffraction