{"id":4784,"date":"2024-12-30T20:50:11","date_gmt":"2024-12-30T20:50:11","guid":{"rendered":"https:\/\/www.richardmudhar.com\/blog\/?p=4784"},"modified":"2025-01-13T11:22:29","modified_gmt":"2025-01-13T11:22:29","slug":"paramagnetism-revisited","status":"publish","type":"post","link":"https:\/\/www.richardmudhar.com\/blog\/2024\/12\/paramagnetism-revisited\/","title":{"rendered":"Paramagnetism revisited"},"content":{"rendered":"

Been nearly ten years since I last looked at this<\/a>. Most people’s interest in paramagnetism seemed to be soil testing with the Phil Callahan Soil Meter (PCSM), mine was investigating megalithic sites. I have Fabrice <\/a>to thank for this and much useful information about the PCSM. I had unsatisfactory results in the field, lacking sensitivity. This was probably due to a bad choice of coil design. Looking at Bartington’s MS2D surface scanning probe, it’s clear I should have designed this more like a metal detector search coil.<\/p>\n

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Bartington’s MS2D surface scanning probe shows how it’s done<\/figcaption><\/figure>\n

Which explains why I shelved this project after dismal results at Gors-Fawr I recall.<\/p>\n

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Gors Fawr measurement fail. I expected this value to be a lot higher<\/figcaption><\/figure>\n

Sadly Philip Callahan passed in November 2017, it seems interest has dropped away without such an eloquent protagonist. For the first time i though I would look at soil, which you can enclose in a solenoid, which takes away a lot of the handwaving. I bought some rock dust from Allgood Farm on ebay<\/a> and thought I’d investigate. Before we go on I should emphasise that Allgood don’t say anything about paramagnetism in their description –<\/p>\n

Volcanic rock dust is rich in essential minerals and trace elements like magnesium, iron, and calcium that plants need to grow.
\nSlow Release: These minerals are released slowly over time, providing a long-term nutrient supply.<\/p><\/blockquote>\n

so this is about mineralisation, not paramagnetism. The last volcanic activity in Britain was 50 million years ago<\/a>, so volcanic rock from the UK won’t be highly paramagnetic, because much will have eroded over 50mn years \ud83d\ude09<\/p>\n

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the sample was tested inside the coil, separated for clarity in the picture<\/figcaption><\/figure>\n

I used a discrete component Franklin oscillator. I am also testing a LM358 oscillator, on the same breadboard<\/p>\n

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opamp and discrete Franklin oscillators on a solderless breadboard<\/figcaption><\/figure>\n

It’s tasteless as hell to make these oscillators on a breadboard, but the discrete component oscillator had a tendency to squegging at these low frequencies so it helped debug that. I have this on DL4YHF’s Spectrum Lab<\/p>\n

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DL4YHF’s Spectrum Lab trace, 30Hz span<\/figcaption><\/figure>\n

and you can see there’s some scintillation, whether this can be improved by building this on Veroboard remains to be seen. Using Spectrum Lab I measured the frequency f2 at 5.4886 kHz and f1 with sample at 5.4861 kHz.<\/p>\n

Using \u03c7 = (f1\u00b2-f2\u00b2)\/(f1\u00b2 \u00d7 4 \u03c0) from last time<\/a>1<\/a><\/sup> I infer the susceptibility is<\/p>\n

(5488.6\u00b2 – 5486.1\u00b2)\/(5488.6\u00b2 \u00d7 4 \u03c0) = 7.25E-05 = 72 \u00b5CGS. Probably +\/- 5\u00b5CGS given the scintillation in frequency. Definitely paramagnetic, probably not stupendously so. I need to find some powdered materials to calibrate this with. And test the Franklin discrete component oscillator and the LM358 version for stability when soldered, rather than bodged on a breadboard \ud83d\ude09<\/p>\n

My coil was ~1.2mH and resonated at ~5.5 kHz with a 1 \u00b5F mylar capacitor and the stray coupling\u00a0 capacitors of the Franklin oscillator. To be continued<\/p>\n

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    \n
  1. \nNote the \u03c7m<\/sub> terminology then<\/a> is wrong, it should be \u03c7v<\/sub>, the dimensionless volume susceptibility ↩<\/a>\n<\/li>\n<\/ol>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

    Been nearly ten years since I last looked at this. Most people’s interest in paramagnetism seemed to be soil testing with the Phil Callahan Soil Meter (PCSM), mine was investigating megalithic sites. I have Fabrice to thank for this and much useful information about the PCSM. I had unsatisfactory results in the field, lacking sensitivity. … Continue reading “Paramagnetism revisited”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":4791,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[57,275,400],"tags":[309],"class_list":["post-4784","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-electronics","category-greenmantle","category-megalithic","tag-paramagnetism"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/www.richardmudhar.com\/blog\/wp-content\/uploads\/2025\/01\/gors-fawr-circle.jpg?fit=1920%2C1440&ssl=1","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p5aOO7-1fa","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/posts\/4784","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/comments?post=4784"}],"version-history":[{"count":6,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/posts\/4784\/revisions"}],"predecessor-version":[{"id":4796,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/posts\/4784\/revisions\/4796"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/media\/4791"}],"wp:attachment":[{"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/media?parent=4784"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/categories?post=4784"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.richardmudhar.com\/blog\/wp-json\/wp\/v2\/tags?post=4784"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}