Large-coil Parietal Repetitive Transcranial Magnetic Stimulation (rTMS) for Alzheimer Disease (AD)

The goal of this clinical trial is to learn if using large-coil (or "deep") repetitive transcranial magnetic stimulation (rTMS) targeting the precuneus and surrounding areas is feasible, tolerable, and potentially efficacious for memory in Alzheimer's Disease. Previous work studying rTMS in Alzheimer's is mixed, but recent work studying rTMS of the precuneus is encouraging for both its short-term and long-term effects. The main questions this study aims to answer are: * Is deep rTMS of the precuneus feasible and tolerable in Alzheimer's? * Are there signs of positive brain changes in response to deep rTMS? * Is deep rTMS potentially efficacious for memory in Alzheimer's? Researchers will compare active stimulation to placebo stimulation while obtaining memory testing and measurements of the brain (imaging, scalp electrode measurements, bloodwork) to see if active treatment works to treat Mild Cognitive Impairment (MCI) and mild-to-moderate dementia due to Alzheimer's disease. Participants will: * Engage with memory testing, brain scans, and bloodwork during a comprehensive assessment * Visit the clinic 3 times for 12 consolidated rTMS sessions, followed by 8 once weekly maintenance visits * Be offered a full open-label active treatment course after completing their treatment course if they are initially in the placebo group