Question

{"given":"The question provides four chemical compounds: Fe₂O₃, Cr₂O₃, Fe₃O₄, and CrO₂. The task is to identify which one among these is classified as a ferromagnetic substance based on its magnetic properties in the solid state.","key_observation":"The critical concept required to solve this question is the understanding of different types of magnetic materials, specifically ferromagnetism, antiferromagnetism, and ferrimagnetism. Ferromagnetic substances exhibit strong, permanent magnetism due to the parallel alignment of magnetic moments, while ferrimagnetic substances also show strong magnetism but with unequal antiparallel alignment. Antiferromagnetic materials have equal antiparallel alignment, resulting in no net magnetic moment.","option_analysis":[{"label":"(A)","text":"Fe₂O₃","verdict":"incorrect","explanation":"Iron(III) oxide, commonly known as hematite, is primarily an antiferromagnetic substance. While some forms can exhibit weak ferromagnetism due to spin canting, it is not a classic example of a ferromagnetic material."},{"label":"(B)","text":"Cr₂O₃","verdict":"incorrect","explanation":"Chromium(III) oxide is a well-known antiferromagnetic material. In antiferromagnetic substances, the magnetic moments of adjacent atoms or ions align in an antiparallel fashion, effectively canceling each other out, leading to no net magnetic moment."},{"label":"(C)","text":"Fe₃O₄","verdict":"incorrect","explanation":"Iron(II,III) oxide, or magnetite, is a ferrimagnetic substance. Ferrimagnetic materials exhibit strong magnetic properties similar to ferromagnetic materials, but their magnetic moments are aligned antiparallel with unequal magnitudes, resulting in a net magnetic moment. It is technically distinct from ferromagnetism."},{"label":"(D)","text":"CrO₂","verdict":"correct","explanation":"Chromium(IV) oxide is a well-established ferromagnetic substance. It is widely recognized for its strong ferromagnetic properties and has practical applications, particularly in magnetic recording media like audio and video tapes."}],"answer":"(D)","formula_steps":[]}