{
  "id": "shielding:shielding-mu-metal",
  "collection": "shielding",
  "slug": "high-permeability-alloy",
  "name": "High-permeability alloy (mu-metal) magnetic shielding",
  "summary": "The only material class that meaningfully attenuates power-frequency magnetic fields, and even then typically by a factor of two to five in a retrofit — which is why distance and source correction are preferred.",
  "status": "verified",
  "lastVerified": "2026-08-12",
  "data": {
    "aliases": [
      "mu metal",
      "magnetic shielding",
      "nickel iron alloy"
    ],
    "form": "paneling",
    "attenuation": {
      "value": 3,
      "max": 14,
      "band": "50/60 Hz magnetic; roughly a factor of 1.5–5 in field strength for practical retrofits",
      "sourceIds": [
        "niehs-emf"
      ]
    },
    "targets": [
      "elf-magnetic"
    ],
    "requiresGrounding": false,
    "failureModes": [
      "Performance collapses if the sheet is bent, drilled or mechanically shocked after annealing",
      "Saturates in strong fields, at which point it stops shielding",
      "Only useful for compact, well-defined sources; useless against a whole-house net-current fault",
      "Cost per square metre is orders of magnitude above RF materials for a much smaller benefit"
    ],
    "related": [
      "emitters:transmission-line",
      "quantities:magnetic-flux-density"
    ]
  },
  "sources": [
    {
      "id": "niehs-emf",
      "title": "Electric and Magnetic Fields",
      "publisher": "National Institute of Environmental Health Sciences",
      "url": "https://www.niehs.nih.gov/health/topics/agents/emf",
      "kind": "government",
      "retrieved": "2026-08-12"
    },
    {
      "id": "sbm-2024",
      "title": "Building Biology Evaluation Guidelines for Sleeping Areas (SBM-2024)",
      "publisher": "Institut für Baubiologie + Nachhaltigkeit (IBN)",
      "url": "https://buildingbiology.com/site/downloads/SBM-2024_EVALUATION_GUIDELINES_EN.pdf",
      "year": 2024,
      "kind": "ngo",
      "retrieved": "2026-08-12"
    }
  ],
  "links": {
    "self": "https://emfbase.com/api/shielding/high-permeability-alloy",
    "html": "https://emfbase.com/shielding/high-permeability-alloy",
    "markdown": "https://emfbase.com/shielding/high-permeability-alloy.md",
    "collection": "https://emfbase.com/api/shielding"
  }
}