This study investigates the magnetic order and superconductivity in the iron-based layered La(O₁₋ₓFₓ)FeAs systems. The parent compound, LaOFeAs, is metallic and exhibits anomalies near 150 K in resistivity and magnetic susceptibility. Neutron scattering reveals a structural phase transition below 150 K, changing the symmetry from tetragonal (P4/nmm) to monoclinic (P112/n) at low temperatures. This is followed by the development of long-range SDW-type antiferromagnetic order at ~134 K with a small magnetic moment. Doping with fluorine suppresses both magnetic order and structural distortion, favoring superconductivity. The study shows that the parent compound of these superconductors is a long-range ordered antiferromagnet with a simple stripe-type antiferromagnetic structure. The structural phase transition occurs before the antiferromagnetic phase transition, changing the structure from P4/nmm to P112/n at low temperatures. The magnetic structure is consistent with theoretical predictions, but the observed Fe moment (0.36(5) μB) is much smaller than the predicted value (~2.3 μB per Fe). The disappearance of static antiferromagnetic order and lattice distortion in doped superconducting materials suggests similarities to high-Tc copper oxides. The results indicate that superconductivity in these Fe-based materials occurs in close proximity to a long-range ordered antiferromagnetic ground state, similar to high-Tc copper oxides. The study highlights the importance of understanding the relationship between magnetism and superconductivity in these materials, and suggests that this new class of materials may open new avenues of research.This study investigates the magnetic order and superconductivity in the iron-based layered La(O₁₋ₓFₓ)FeAs systems. The parent compound, LaOFeAs, is metallic and exhibits anomalies near 150 K in resistivity and magnetic susceptibility. Neutron scattering reveals a structural phase transition below 150 K, changing the symmetry from tetragonal (P4/nmm) to monoclinic (P112/n) at low temperatures. This is followed by the development of long-range SDW-type antiferromagnetic order at ~134 K with a small magnetic moment. Doping with fluorine suppresses both magnetic order and structural distortion, favoring superconductivity. The study shows that the parent compound of these superconductors is a long-range ordered antiferromagnet with a simple stripe-type antiferromagnetic structure. The structural phase transition occurs before the antiferromagnetic phase transition, changing the structure from P4/nmm to P112/n at low temperatures. The magnetic structure is consistent with theoretical predictions, but the observed Fe moment (0.36(5) μB) is much smaller than the predicted value (~2.3 μB per Fe). The disappearance of static antiferromagnetic order and lattice distortion in doped superconducting materials suggests similarities to high-Tc copper oxides. The results indicate that superconductivity in these Fe-based materials occurs in close proximity to a long-range ordered antiferromagnetic ground state, similar to high-Tc copper oxides. The study highlights the importance of understanding the relationship between magnetism and superconductivity in these materials, and suggests that this new class of materials may open new avenues of research.