<p>The current study evaluates the antibacterial efficacy and magnetic and microwave spin resonance of Sr²⁺- and Co²⁺-substituted Zr_1-xSr_xFe_2-yCo_yO₄ (0 ≤ x and y ≥ 0.20) ferrite nanoparticles synthesized by low-temperature auto-combustion route. In this regard, various physico-chemical analytical techniques such as XRD, FESEM, EDS, HRTEM, FTIR, and XPS were employed to characterize the structure and composition of Zr_1-xSr_xFe_2-yCo_yO₄ (0 ≤ x and y ≥ 0.20) nanoferrite. The XRD pattern confirms the presence of characteristic diffraction peaks of the cubic spinel structure in agreement with FTIR studies. EDS indicates the existence of Zr, Sr, Co, Fe, and O elements in line with XPS studies. The magnetic behaviour (M-H loop) shows an increase in saturation magnetization <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10948_2025_7016_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="35" /> </InlineMediaObject> <EquationSource Format="TEX">\({^{\prime}M_{S}}^{\prime}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow> <mmultiscripts> <mrow /> <mrow /> <mo>′</mo> </mmultiscripts> <msub> <mi>M</mi> <mi>S</mi> </msub> </mrow> <mrow /> <mo>′</mo> </mmultiscripts> </math></EquationSource> </InlineEquation>, remanent magnetization <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10948_2025_7016_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="33" /> </InlineMediaObject> <EquationSource Format="TEX">\({^{\prime}M_{r}}^{\prime}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow> <mmultiscripts> <mrow /> <mrow /> <mo>′</mo> </mmultiscripts> <msub> <mi>M</mi> <mi>r</mi> </msub> </mrow> <mrow /> <mo>′</mo> </mmultiscripts> </math></EquationSource> </InlineEquation>, and coercive field <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10948_2025_7016_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="30" /> </InlineMediaObject> <EquationSource Format="TEX">\({^{\prime}H_{c}}^{\prime}\)</EquationSource> <EquationSource Format="MATHML"><math> <mmultiscripts> <mrow> <mmultiscripts> <mrow /> <mrow /> <mo>′</mo> </mmultiscripts> <msub> <mi>H</mi> <mi>c</mi> </msub> </mrow> <mrow /> <mo>′</mo> </mmultiscripts> </math></EquationSource> </InlineEquation> with an increase in Sr²⁺ and Co²⁺ ion substitution and a higher value of effective magneto-crystalline anisotropy (<InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10948_2025_7016_Article_IEq4.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="42" /> </InlineMediaObject> <EquationSource Format="TEX">\({K}_{eff})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>K</mi> <mrow> <mi mathvariant="italic">eff</mi> </mrow> </msub> <mrow> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> for Zr_0.80Sr_0.20Fe_1.80Co_0.20O₄. EPR spectra exhibits a broad ferromagnetic resonance signal with a superimposed hump, and the calculated <i>g</i>-value equal to ~ 2.248 is assigned to ferrite Fe³⁺ ions and oxygen vacancies. Zr_0.90Sr_0.10Fe_1.90Co_0.10O₄ sample shows high value of saturation magnetization ~ 26.42&#xa0;emu/g and low spin concentration ~ 2.53 × 10²² spin/g, and can be used effectively in various optoelectronics and spintronic devices The antimicrobial activity was investigated at biocompatible dose against Gram-negative (<i>E. coli</i> and <i>P. aeruginosa</i>) and Gram-positive (<i>S. aureus</i>) bacteria. It can be concluded that the synthesized nanoparticles are active against both Gram-negative and Gram-positive bacteria. This study shows that synthesized nanoparticles (NPs) could be a strong candidate for antibacterial and wound healing nano-drugs.</p> Graphical Abstract <p></p>