The actual magnetic moment shows a large deviation from the spin-only formula in the case of
(a)$\mathrm{Ti}^{+}$
(b)$\mathrm{V}^{3+}$
(c)$\mathrm{Gd}^{3+}$
(d)$\mathrm{Sm}^{3+}$
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
Sm³⁺ (f⁵, ⁶H₅/₂) has low-lying J levels that are thermally populated, so the observed moment (≈1.5 BM) departs strongly from both the spin-only and the ground-J value; Ti³⁺, V³⁺ and Gd³⁺ do not.